Belemnites (Gr. from a dart or arrow), a class of extinct molluscous animals, belonging to the same division as ammonites, termed cephalopods from the organs of motion being arranged around the head. The fossil remains of the animal are met with in the rocks of the upper secondary, and are particularly abundant in the strata of the green-sand formation in New Jersey. The part preserved, often detached from the loose strata, is a pointed cone sometimes eight inches long, of brown color and stony material, resembling in shape the head of a dart or javelin, whence their name. The larger end is hollow, the cavity being of similar shape to that of the whole specimen. They are found by millions in the formations to which they belong, and from 80 to 90 species of them have been recognized. They early attracted the attention of scientific men as well as of the common people; and it appears from the memoir of M. de Blain-ville that no fewer than 91 authors, whose names he gives, beginning with Theophrastus, have written on this subject.
The ancient inhabitants of Asia Minor are represented by some writers to have designated these fossils by the term dactyli Idaei, fingers of Mount Ida, which, however, according to other authorities, was very ditferently applied, some describing these unknown Dactyli as divine persons worthy of worship, as having nursed and brought up the god Jupiter; and others, as Sophocles, making them to be the inventors of the manufacture of iron. Popular modern names for them are thunder stones, devil's fingers, and spectre candles. By the researches of Dr. Buckland and Prof. Agassiz the true nature of the belemnites has been fully established. The hollow pointed body is composed of carbonate of lime, part of which was the original fibrous shell, and the remainder introduced by infiltration. Thus the fossil became crystalline and nearly solid. The cavity was the receptacle of the animal, but, as in the genera bulla and sepia, and the coralline zoophytes, it by no means covered the fleshy portions; these, on the contrary, extended outside of the shell, and enclosed it, very much as a skeleton is enclosed and covered with the softer portions of the body.
Within this cavity was the apparatus of the air chambers and siphon, common also to the ammonite, nautilus, and other chambered shells, by means of which the animal could rise or sink at will. But the belemnites also were provided with the ink-bag apparatus of the modern sepia; an important protection for their soft bodies, unguarded as they were by any outer shell. These ink bags were noticed in a communication by Dr. Buckland to the geological society of London in 1829, as found by him in a fossil state, which he supposed, from comparison with known molluscous animals furnished with them, must have belonged to dibranchiate or two-gilled cephalopods connected with belemnites. Subsequently Prof. Agassiz met with specimens retaining the ink bag within the cavity; and the fact being thus established, the name belemnosepia was thereupon given to the family in the class of cephalopods comprising all the species of belemnites. From the immense numbers of these animals, and also of the still more abundant varieties of ammonites, which flourished during the periods of the formation of the oolite and cretaceous groups, Dr. Buckland infers that these extinct families filled a larger space and performed more important functions among the inhabitants of the ancient seas than are assigned to their few living representatives in our modern oceans.
Belemnites restored, after D'Orbigny.
Belemnites restored by Owen.