CEPHALOPODA. 



No. 173. [463, Cast]. Beloteuthis subcostata, Munst. 



OssELET. This flattened Calamary receives its gen- 

 eric name from its supposed affinity to the living Squid. 

 The osselet, or rudimental shell, represented in this 

 specimen, is broad and rounded at each end, and in its 

 form approaches nearly to the osselet of the living 

 Sepia of the Mediterranean. It was found in the Lias 

 at Holzmaden, Wurtemberg. 



Size, 6x3. 



oa 



No. 174. 



), Cast]. Belemnosepia 



Agassiz. 



An undescribed species. The osselet of this genus is charac- 

 terized by a wide shaft, and is frequently accompanied by a well- 

 preserved ink-bag. This specimen shows the muscular tissues of 

 the body, fins and arms, with traces of the non-nacreous pen. It 

 is from the Oxford Clay (Middle Oolite), Christian Malford, Eng- 

 land, and is in the private Geological Cabinet of Mr. "Ward, 

 Rochester. Size, 10 x 4. 



No. 175. [456, Cast]. Belemnites Owenii, Pratt. 



Guard. The Belemnite is the most complicated of Cephalopod 

 shells. The chambered part, ov phragmocone, is a straight, attenu- 

 ated cone with numerous septa, resembling a pile of watch-gias.ses, 

 concave towards the base. The whole is enveloped in a sheath ; 

 and the two together are lodged in a conical cavity or alveolus, 

 excavated in the base of a long spathose body (corresponding to 

 the mucro of the cuttle-bone), resembling the head of a javelin, 

 whence the generic name. The exterior of this "guard," as it is 

 called, has usually a longitudinal groove; and the septa of the 

 phragmocone are perforated by a marginal siphuncle generally 

 situated on the side nearest the groove; but in certain species, 

 characterized by a flattened guard, the siphuncle is on the opposite 

 side. Besides these fossil parts, there have been found remains 

 of the ink-bag, pen, mantle, mandibles, arms and hooks. The 

 Belemnitidse culminated in the Mesozoic. This specimen, now 

 in the Ward Collection of the University of Rochester, is from 

 the Oxford Clay (Upper Oolite), at Christian Malford, England. 

 The fractured upper portion shows the alveolar cavity with the phragmocone 

 in place. Size, 6 x 3. 





