298 MOLLUSCA. 



of its anatomy. Thus we know that the body was furnished 

 with lateral fins, that there were eight arms and two longer 

 " tentacles," that the suckers were provided with horny hooks, 

 that there was a large ink-sac, and that the mouth was armed 

 with horny mandibles. 



The following table of the sections and sub-sections of the 

 species of the genus Belemnites is the one given by Dr S. P. 

 Woodward : 

 Section I. Acceli. 



Without dorsal or ventral grooves. 

 Sub-section I. Acuarii. 



Without lateral furrows, but often channelled at the extreme 



point. (Ex. B. acuarius. Lias.) 

 Sub-section 2. Clavati, 



With lateral furrows. (Ex. B. clavatus. Lias.) 

 Section II. Gastrocoeli. 



Ventral groove distinct. 

 Sub- section I. Canaliculati. 



No lateral furrows. (Ex. B. canaliculatus. Inf. Oolite.) 

 Sub-section 2. Hastati. 



Lateral furrows distinct. (Ex. B. hastatus. Oolite.) 

 Section III. NotoccelL 



With a dorsal groove, and furrowed on each side. (Ex. 

 B. dilatatus. Neocomian. ) 



The species of the genus Belemnites range from the top of 

 the Trias, where the earliest forms appear, to the 

 Upper Greensand, in which the genus finally dis- 

 appears. The species are most numerous in the 

 Jurassic Rocks, and often occur in the greatest 

 abundance in particular beds or particular localities. 

 It would seem not improbable that the genus Belop- 

 tera, before noticed, should be referred to the Belem- 

 nitidte, and the genus Bekmnosepia (or Geoteuthis), 

 formerly referred to the Tcuthidce, appears to be al- 

 most certainly referable here. 



b. Belemnitella. In this genus (fig. 267) the skele- 

 ton is very similar in its general arrangement to that 

 of Belemnites ; but there is a straight fissure in the 

 guard, at its upper end, on the ventral side of the 

 wall of the alveolus. The species of this genus are 

 _ exclusively Cretaceous, and are only found in the 



per portion of this formation, ranging from the 



c. Belemnoteiithis. " Shell consisting of a phrag- 

 maeonc, like that of the Belemnite ; a horny dorsal pen with 

 obscure lateral bands ; and a thin fibrous guard, with two 

 diverging ridges on the dorsal side. Animal provided with 



