Eighty-eight species of Belemnites have already been discovered;* and the vast numerical amount to which individuals of these species were extended, is proved by the myriads of their fossil remains that fill the Oolitic and Cretaceous formations. When we recollect that throughout both these great formations, the still more numerous extinct family of Ammonites is co-extensive with the Belemnites; and that each species of Ammonite exhibits also contrivances, more complex and perfect than those retained in the few existing cognate genera of Cephalopods; we cannot but infer that these extinct families filled a larger space, and performed more important functions among the inhabitants

calcareous plates, alternating with horny plates, which form the shield and shallow cup of the Sepiostaire, (Pl. 44′, Fig. 2, e. and Fig. 5. e.,) represent the hollow fibro-calcareous cone or cup of the Belemnite, surrounding its alveolus.

The margin of the horny plates; interposed between the calcareous plates of the shield and cup of the Sepiostaire, (Pl. 44′, Fig. 4, e, e, e', e.,) represents the horny marginal cavity of the cone of the Belemnite, beyond the base of its hollow calcareous cone, (Pl. 44′ Fig. 7, e. e'. e".) This horny sheath of the Belemnite was probably formed by the prolongation of the horny lamine which were interposed between its successive cones of fibrocalcareous matter.

The chambered alveolus of the Belemnite is represented by the congeries of thin transverse plates, (Pl. 44', Fig. 4, b.) which occupy the interior of the shallow cup of Sepiostaire, (e. e'.;) these plates are composed of horny matter, penetrated with carbonate of lime.

The hollow spaces between them, (Fig. 5, b, b',) which are nearly a hundred in number in the full grown animal, act as air chambers to make the entire shell permanently lighter than water; but there is no siphuncle to vary the specific gravity of this shell; and the thin chambers between its transverse plates are studded with an infinity of minute columnar, and sinuous partitions, planted at right angles to the plates, and giving them support. (Fig. 6', 6", 6"".)

The absence of a siphuncle render, the Sepiostaire an organ of more simple structure, and of lower office, than the more compound shell of Belemnite.

⚫ (See index to M. Brochant de Villiers' Translation of De la Beche's Manual of Geology.)

of the ancient seas, than are assigned to their few living representatives in our modern oceans.

Conclusion.

It results from the view we have taken of the zoological affinities between living and extinct species of chambered shells, that they are all connected by one plan and organization; each forming a link in the common chain, which unites existing species with those that prevailed among the earliest conditions of life upon our globe; and all attesting the Identity of the design, that has effected so many similar ends through such a variety of instruments, the principle of whose construction is, in every species, fundamentally the same.

Throughout the various living and extinct genera of Chambered shells, the use of the air-chambers and siphon, to adjust the specific gravity of the animals in rising and sinking, appears to have been identical. The addition of a new transverse plate within the conical shell added a new air-chamber, larger than the preceding one, to counterbalance the increase of weight that attended the growth of the shell and body of all these animals.

These beautiful arrangements are, and ever have been, subservient to a common object, viz. the construction of hydraulic instruments of essential importance in the economy of creatures destined to move sometimes at the bottom, and at other times upon or near the surface of the sea. The delicate adjustments whereby the same principle is extended through so many grades and modifications of a single type, show the uniform and constant agency of some controlling Intelligence; and in searching for the origin of so much method and regularity amidst variety, the mind can only rest, when it has passed back, through the subordinate series of Second causes, to that great First Cause, which is found in the will and power of a common Creator.

SECTION VIII.

FORAMINATED POLYTHALAMOUS SHELLS.

Nummulites.

Ir the present were a fit occasion for such minute inquiries, the investigations of the various known species of Microscopic shells would unfold a series of contrivances. having relation to the economy of the minute Cephalopods by which they were constructed, not less striking than those we have been examining in the shells of extinct Genera and species of larger Cephalopods. M. D'Orbigny has noticed from 600 to 700 species of these shells, and has prepared magnified models of 100 species, comprehending all the Genera.*

The greater number of these shells are microscopic, and swarm in the Mediterranean and Adriatic. Their fossil species abound chiefly in the Tertiary formations, and have hitherto been noticed principally in Italy. (See Soldani, as

* M. D'Orbigny, in his classification of the shells of Cephalopodous Mollusks, has established three orders. 1. Those that have but a single chamber, like the shell of the sepia and horny pen of the Loligo. 2. Polythalamous shells, which have a siphuncle passing through all the internal chambers, and which terminate in a large external chamber, beyond the last partition, such as Nautili, Ammonites, and Belemnites. 3. Polythalamous internal shells, which have no chamber beyond their last partition.

Shells of this order have no siphuncle, but the chambers communicate with each other by means of one or many small foramina. On this distinction he has founded his Order Foraminiferes, containing five families and fifty-two genera.

It may be necessary to apprize the reader that doubts have been enter. tained as to the cephalopodous structure of some of these minute multilocular shells; and that there are not wanting those who attribute to them á different organization.

quoted at page 97 of this volume.) They occur also in the Chalk of Meudon, in the Jura Limestone of the Charente inferieure, and the Oolite of Calne. They have been found by the Marquis of Northampton in Chalk flints from the neighbourhood of Brighton.

The Nummulite is the only Genus I shall select on the present occasion from this Order. It is included in M. D'Orbigny's Section Nautiloids.

Nummulites (Pl. 44, Fig. 6, 7,) are so called from their resemblance to a piece of money, they vary in size from that of a crown piece to microscopic littleness; and occupy an important place in the history of fossil shells, on account of the prodigious extent to which they are accumulated in the later members of the Secondary, and in many of the Tertiary strata. They are often piled on each other nearly in as close contact as the grains in a heap of corn. In this state they form a considerable portion of the entire bulk of many extensive mountains, e. g. in the Tertiary limestones of Verona and Monte Bolca, and in secondary strata of the Cretaceous formation in the Alps, Carpathians, and Pyrenees. Some of the pyramids and the Sphinx, of Egypt, are composed of limestone loaded with Nummulites.

It is impossible to see such mountain-masses of the remains of a single family of shells thus added to the solid materials of the globe, without recollecting that each individual shell once held an important place within the body of a living animal; and thus recalling our imagination to those distant epochs when the waters of the ocean which then covered Europe were filled with floating swarms of these extinct Mollusks, thick as the countless myriads of Beröe and Clio Borealis that now crowd the waters of the polar seas.*

* We have an analogy to this supposed state of crowded population of Nummulites in the ancient sea, in the marvellous fecundity of the northern ocean at the present time. It is stated by Cuvier, in his memoir on the VOL. 1.-25

The Nummulites, like the Nautilus and Ammonite, are divided into air-chambers, which served the office of a float: but there is no enlargement of the last chamber which could have contained any part of the body of the animal. The chambers are very numerous, and minutely divided by transverse plates; but are without a siphuncle. The form of the essential parts varies in each species of this genus, but their principles of construction, and manner of operation, appear in all to have been the same.

The remains of the Nummulites are not only animal bodies which have contributed to form the calcareous strata of the crust of the earth; other, and more minute species of Chambered shells have also produced great, and most surprising effects. Lamarck (Note, v. 7. p. 611,) speaking of the Miliola, a small moltilocular shell, no larger than a millet seed, with which the strata of many quarries in the neighbourhood of Paris are largely interspersed, notices the important influence which these minute bodies have exercised by reason of their numerical abundance. We scarcely con

Clio Borealis, that in calm weather, the surface of the water in these seas swarms with such millions of these mollusks (rising for a moment to the air at the surface, and again instantly sinking towards the bottom,) that the whales can scarce open their enormous mouths without gulping in thousands of these little gelatinous creatures, an inch long, which, together with Medusa, and some smaller animals, constitute the chief articles of their food; and we have a farther analogy in the fact mentioned in Jameson's Journal, vol. ii. p. 12. "That the number of small Medusa in some parts of the Greenland seas is so great, that in a cubic inch, taken up at random, there are no less than 64. In a cubic foot this will amount to 110,592; and in a cubic mile (and there can be no doubt of the water being charged with them to that extent,) the number is such, that allowing one person to count a million in a week, it would have required 80,000 persons, from the crea tion of the world, to complete the enumeration."-See Dr. Kidd's admirable Introductory Lecture to a course of Comparative Anatomy, Oxford, 1824, p. 35.

* In Pl. 44, Figs. 6, 7, sections of two species of Nummulite are copied from Parkinson. These show the manner in which the whorls are coiled up round each other, and divided by oblique septa.