S6 



BRITISH BELEMNITES. 



alveolar region expanded, covered with rough granulations ; post-alveolar region enlarged. 

 The grooves are distinct for about half an inch each. 



Only one specimen is known, viz. "No. 976," in the Whitby Museum, of which 

 PI. XX, fig. 51, is a sketch. The total length is 7^ inches, the diameter at the apex of 

 the phragmocone less than 0-4 inch, giving a proportion of axis (as 1800 to 100 diameter) 

 such as occurs in Belemnites clavaius and other very long Belemnites. In the post- 

 alveolar enlargement the diameter becomes 0-45 inch. 



Localiiy. Obtained by J\lr. Simpson from the upper part of the Lower Lias, on the 

 north side of Robin Hood's Bay. 



Ohservations. It is very possible, indeed very likely, that by further research it may 

 be proved that this really elegant Belemnite is a full-grown example of one of the claviform 

 shells which occur in the Lower Lias of Yorkshire. With a view to settle this and 

 some other questions, I have examined four times the beds which yield these Belemnites at 

 the base of HuntclifF, collecting many specimens ; and Mr. P. Cullen has with equal care 

 explored for me the corresponding beds of Robin Hood's Bay. At present, looking on a 

 hundred specimens, I am not able to furnish evidence in favour of the opinion. 

 Mr. Simpson formerly included it with less hastate forms in the species he called 

 B. elegans, but the great proportionate length of its axis is probably decisive against that 

 alliance. The rugulosity about the alveolar region may be of some importance as a 

 character, and yet not really diagnostic, just as in B. tubularis another kind of rugulosity 

 is frequently but not constantly found on the alveolar region. 



Belem:^ites ctlindiiicus, Sin/jjson. PI. XX, fig. 5.2, P. /, P. v, P. d. 



Reference. Belemnites cylindricus, Simpson, ' Lias Fossils,' No. 27, 1855. 



Guard (old). Cylindrical in the alveolar region, tapering evenly to a rather blunt, 

 often rather recurved summit, from which two distinct short dorso-lateral grooves proceed, 

 and lose themselves before reaching the alveolar region. In a very perfect specimen the 

 apex is striated on the ventral and on the dorsal surface ; the ventral striae are accompanied 

 by a short groove, not seen in any other example. 



Sections show a nearly circular contour, with the axis a httle excentric and straight. 

 The ventral face is sometimes a little flattened (ventro-planate, as in B. ventropJanus and 

 B. subdej)ressus of Voltz) . 



Greatest length observed (including an expanded part), 6 inches, of which the 

 axis of the guard occupies 4 ; diameter of the cylindrical part, y^ths of an inch. 



Young specimens are rarely seen, and are more pointed than old ones, and show hardly 

 a trace of apicial grooves or stria3. 



