CEPHALOPODA. 173 



DOSIDICTJS, Stp. 1856. 



Somewhat like Ommastrephes. Lower portion of arms with 

 large suckers, and the extremity with numerous small suckers. 

 Tentacles with four or fiye hooks. 



Distribution, 1 species. Mediterranean. , 



Family IY. — ^BELEMisriTiDiE. 



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 siphunde, close to 

 the ventral side. 



Belemkites, Lamarck. 1801. ' 



Etymology, helemnon, a dart.* 



Example, B. puzosianus, PL 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 beyond its rim, in the 

 form of sword-shaped processes (PL II., Pig. o).-j- Guard 

 fibrous, often elongated and cylind] ical ; becoming very thin in 

 front, where it invests the phragmocone. J 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 lithos, a stone) was formerly given to all fossil genera. 



t Eive specimens -w^er.e at one time in Dr. Mantell's cabinet, and others are in the 

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

 Malford, Wilts. A still finer specimen, in Mr. Montefiore's collection, was recently 

 obtained from the has of Dorsetshire by Mr. Day. 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-hag. The phragmocone of a specimen 

 corresponding to this in size measures 7f inches in length, 



X The specific gravity of the guard is identical with that of the sheU 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 mucro 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 



Pinna, recent, from the Mediterranean 

 Trichites plottii, from the inferior oolite 



Conus monile, recent 



Conus ponderosus, Miocene, Touraine ... 



2,677 

 2,607 

 2,670 

 2,010 

 2,713 



