CEPHALOPODA. 173 



DosiDicus, Stp. 1856. 



Somewhat like Ommastre2:)lies. Lower portion of arms witJt 

 large suckers, and the extremity with numerous small sucker^ 

 Tentacles with four or fiye hooks. 



Distribution, 1 species. Mediterranean. 



Family IY.— Belemnitid.^. 



Shell consisting of a jpen, terminating posteriorly in a cham- 

 bered cone, sometimes invested with a fibrous guard. The air- 

 cells of the phragmocone are connected by a si^jliuncle, close to 

 the ventral side. 



Belemnites, Lamarck. 1801. 



Etymology, helemnon, a dart.* 



Example, B. puzosianus, PL II., Fig. 5. 



PJiragmocone horny, slightly nacreous, with a minute globular 

 nucleus at its apex ; divided internally by numerous concave 

 sejjta. Pen represented by two nacreous bands on the dorsal 

 side of the phragmocone, and j)roduced beyond its rim, in the 

 form of sword-shaped processes (PI. II., Fig. 5).t Guard 

 fibrous, often elongated and cylindi ical ; becoming very thin in 

 front, where it invests the phragmocone. | Suckers provided 

 with horny hooks. 



More than 100 species of belemnites have been found in a 

 fossil state, ranging from the lias to the chalk, and distributed 

 over all Europe. A few species have been found in the chalk 



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

 t Five specimens were at one time in Dr. Mautell's cabinet, and others are in the 

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

 jMalford, Wilts. A still finer specimen, in Mr. Montefiore's collection, was recentlj 

 obtained from the lias of Dorsetshire by Mr. Day. The last chamhcr of a lias 

 belemnite in the British Museum is 6 inches long, and 2^ inches across at the smallei 

 «id ; a fracture near the siphuncle shows the ink-hag. The fhragmocone of a specimec 

 corresponding to this in size measiu'es 7|- inches in length. 



X The specific gi'avity of the guai-d is identical with that of the shell of the receni 

 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 mucro of tin 

 sepiostaire, with which alone it is homologous, is quite as dense as the belemnite. \^'t 

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

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



Belemnites puzosianus, Oxford clay 2,674 



Belcmnitella mucronata, chalk 2,077 



Pinna, recent, from the Mediterranean 2,(J07 



Trichites plottii, from the inferior oolite 2,670 



Conus monile, recent 2,910 



Conus ponderosus, Miocene, Touraine 2,713 



