CEPHALOPODA. 73 



The sagittated calamaries are gregarious, and frequent tlie open sea in all 

 climates. They are extensively used in the cod-fishery off Newfoundland, and 

 are the principal food of the dolphins and cachalots, as well as of the albatross 

 and larger petrels. The sailors call them "sea-arrows" or "flying squids," 

 from their habit of leaping out of the water, often to such a height as to fall 

 on the decks of vessels. They leave their eggs in long clusters floating at the 

 surface. 



Distr., 14 recent sp. ; similar ;?<?;m (4 sp.) have been found fossil in the 

 Oxford clay, Solenhofen ; it may, however, be doubted whether they are ge- 

 nerically identical. 



TAlSriLY IV. Belemnitid^. 



Shell consisting of a pe7i, terminating posteriorly in a chambered cone, 

 sometimes invested with a ^hrovi?, guard. The air-cells of 'Ca^ i:iliragrao-cone 

 are connected by a slpkuncle, close to the ventral side. 



Belemnites, Lamarck. 1801. 



Ettjm., helemnon, a dart.* 



Hx., B. puzosianus, pi. II., fig. 5. 



Phragmocone horny, slightly nacreous, with a minute globular nucleus at 

 its apex ; divided internally by numerous concave septa. Pen represented by 

 two nacreous bands on the dorsal side of the phragmocone, and produced be- 

 yond its rim, in the form of sword-shaped processes (pi. II., fig. 5).t Guard, 

 fibrous, often elongated and cylindrical ; becoming very thin in front, where 

 it invests the phragmocone. J 



Nearly 100 species of belemnites have been found in a fossil state, ranging 

 from the lias to the gault, and distributed over all Europe. The phragmocone 

 of the belemnite, which represents the terminal appendix of the calamaries, is 



* The termination ties (from lifhos, a stone) was formerly given to all fossil genera. 

 t The most perfect specimens known are in the cabinet of Dr. Mantell, and the 

 British Museum ; they were obtained by William Buy in the Oxford clay of Christian 

 Malford, "Wilts. The last chamber of a lias belemnite in the British Museum is 6 

 inches long, and 2| inches across at the smaller end; a fracture near the siphuncle 

 shows the ink-bag. The phragmocone of a specimen corresponding to this in size, 

 measures 7| inches in length. 



X The specific gravity of the guard is identical with that of the shell of the recent 

 pinna, and its structure is the same. Parkinson and others have supposed that it was 

 originally a light and porous structure, like the cuttle bone ; but the nmcro of the 

 sepiostaire, with which alone it is homologous, is quite as dense as the belemnite. We 

 are indebted to Mr. Alex. Williams, M.R.C.S., for the following specific gravities of 

 recent and fossil shells, compared with water as 1,000 : — 



Belemnites puzosianus, Oxford clay 2,674 



Belemnitella mucronata, chalk 2,677 



Pinna, recent, from the Mediterranean 2,607 



Trichites plottii, from the inferior oolite 2,670 



Conus monile. recent 2,910 



Conus ponderosus, Miocene, Touraine 2,713 



E 



