46 BELEMNITID^. 



A. Ill many Belemnites the extension of the conotheca seems 

 to run out in one simple broad plate, as in B. hastatus, from 

 Solenhofen (ii, 22). 



B. In Belemnites Puzosianus^ d'Orbigny, the pro-ostracum is 

 very thin, and apparently horny or imperfectly calcified in the 

 dorsal region, supported laterally by two long, narrow, parallel, 

 calcareous plates (B. Puzosianus from the Oxford 'day, ii, 20). 

 Professor Huxley considers this difference between the pro- 

 ostraca of generic importance. 



C. The third kind of pro-ostracum is exhibited by Orthoceras 

 elongata, Be la Beche, the type of the genus Xiphoteuthis, 

 Huxley. It is calcareous-, and is composed of concentric lamellae, 

 each of which consists of fibres disposed perpendicularly to the 

 plane of the lamella; the phragmocone is very long and narrow, 

 and the guard cylindroidal. 



Professor Huxley suspects that a 'thoroughly well-preserved 

 specimen of Belemnoteuthis will some daj^ demonstrate the exist- 

 ence of a fourth kind of pro-ostracum among the Belemnitidse. 



" The Acanthoteuthes of Munster, so far as they are known 

 only by hooks and impressions of soft parts, may have been 

 either Belemnites, or Belemnoteuthis, or Plesioteuthis, or may 

 have belonged to the genus Celoeno." — Huxley. 



The genus Belopeltis, Voltz, was founded on the pro-ostraca 

 of Belemnites. 



The genus Actinocamax, Miller, was founded on the guards 

 of Belemnites and Belemnitella, the upper parts of which had 

 decayed, and thus presented no alveolar cavity. -^Woodward. 



Belemnites, Lamarck. 



Etym. — Belemnon^ a dart. 



Syn. — Diploconus, Zittel, 1868 Actinocamax, Voltz, 1840. 

 Gastrosiphites, Notosiphites and Pseudobelus, Duval. 



Distr. — 100 sp., fossil only. B. excentricus, Keferst. (xxviii, 72). 



Animal, arms and tentacles with two rows of horny hooks. 

 Shell, phragmocone horny and slightl}^ nacreous, with a minute 

 globular initial chamber ; two nacreous bands on its dorsal side, 

 and produced beyond its rim into sword-shaped processes, 

 represent the rostrum, which is fibrous, cylindrical, thickened 

 behind, thin in front where it invests the phragmocone. 



These animals, supposed to have been gregarious, from the 

 number of their remains found in certain localities, were very 

 numerovis in species, over 100 having been described from the 

 liassic and chalk formations of Europe, from the chalk of South- 

 ern India, from the Jurassic of the Himalayas, etc. 



The phragmocone is ver3^ delicate, and its preservation is 

 usually due to the infiltration of calcareous spar into its cham- 

 bers. M. d'Orbigny supposes that the variation of tlie propor- 



