258 ORGANIC REMAINS. 



No. 1, PI. XIV, is the most common of our belemnites. It 

 abounds in the alum shale, and in the calcareous sandstone ; though in 

 the latter, as also in the dogger, the belemnite has in many instances 

 been decomposed, and nothing but the cast left. The cast is of a 

 singular description; the radiated part, or sheath, being entirely gone, 

 and its place left empty, while the cast of the chambered part, or 

 alveolus, projects into the oblong cavity. The specimen figured has 

 a great part of the alveolus laid bare, exposing the edges of the cups. 

 Fig. 3 is a longitudinal section, shewing the manner in which the 

 point of the alveolus terminates in its radiated sheath. This belem- 

 nite is sometimes ten or twelve inches long, and two inches across, 

 at the broad end. It is seldom quite round, being generally some- 

 what flattened on two opposite sides, so that its section is oval rather 

 than circular. This compression is usually greatest near the point, 

 from which a slight groove runs a little way along each of the flatten- 

 ed sides. Sometimes a third groove is seen on one of the intermediate 

 spaces, which is often a little flattened, and in a few instances a fourth 

 groove appears on the side opposite. — This species is named by 

 Sowerby (Tab. 60. Fig. 1,2, 3) orthocera conica, from the conical 

 form of the alveolus, a circumstance not peculiar to this species. As 

 it is the most common species, we may name it belemnites vulgaris. 

 The mutilated form in which it commonly occurs, may be seen in the 

 specimens figured in the mass of encrinite, PI. V, Fig. 6. 



No. 4, PI. XIV, is a species nearly allied to No. 1. It differs 

 from it, in being generally more blunt and more angular. It has one 

 side very flat, the opposite side rounded, and the two intermediate 

 spaces partially compressed. We usually find on each of those two 

 sides a slight groove at the point, and on the flat side an oblong de- 

 pression rounded at one end, as represented in the Figure. The 

 apex of the alveolus, which is nearly central in No. 1, always inclines 

 in this species to the flat side ; as is shewn in the section, Fig. 5 ; 



