BELEMNITES OF THE LIAS. 



57 



The fossils so depicted come from the Upper Lias ; they have distinct ventral and dorso- 

 lateral grooves. 



Several of these Yorkshire forms have been described by Simpson (Lias Fossils, No. 

 9, 10, 11, 12, 16), but not figured. 



In the cliffs of Dorsetshire, about Lyme Regis, Charmouth, and Seatown, a con- 

 siderable number of Belemnites occur corresponding to these in length, general form, 

 and compression ; some are deficient of grooves near the apex, and others show 

 them more or less ; but striation about the apices, if not wholly absent, is not syste- 

 matically present. The surface of the Dorsetshire Belemnites is not always perfectly 

 preserved; it is often somewhat eroded. I have, however, succeeded in identifying 

 a few specimens with one of the Yorkshire fossils. Besides this, the sides are 

 usually channelled or marked by plane facets, so as to produce on the whole a 

 different aspect to the eye. Some of these forms from the Dorsetshire Lias are given on 

 PI. XIIL 



After examining as many specimens as I could extract from the Lias near Whitby, 

 and others from Robin Hood's Bay, collected for me by Mr. Peter Cullen, I have 

 thought it desirable to employ separate names for four forms which offer available 

 characters, and perhaps further search may prove them to be really distinct ; but it will 

 be often very useful to employ for them all collectively the general term of gracilesT 

 There is one allied form in the Lower Lias of Yorkshire. 



Belemnites l^evis, Simpson. PI. X, figs. 23, 26. 



Reference. Belemnites Icevls, Simpson, Lias Fossils, No. 9, p. 25, 1855. 



Belemnites trivialis, Simpson, Lias Fossils, No. 11, p. 26. 



Guard. Compressed ; elongate ; tapering uniformly, and at last rather suddenly, 

 to the apex, which is occasionally crested, plaited, or striated, without distinct grooves on 

 any face. Sections show the contour to be eUiptical, with a slightly excentric, nearly 

 straight axis. 



Dimensions. Greatest length observed of the guard alone 4 inches, beyond which 

 the conotheca, converted into bisulphide of iron, is traced 1 inch. 



Proportions. The diameter, v d, at the apex of the phragmocone, being taken at 

 100, the cross diameter is 88, the ventral radius 44, the dorsal 56, the axis 350 to 500. 



Phragmocone. a little arched, ending in a spherule, with septa occupying a length 

 equal to that of the axis of the guard. 



Locality. Jet-rock of the Upper Lias, Whitby, rather plentiful {Simpson) ; also 

 above the Jet-rock at Whitby and Robin Hood's Bay [Phillips). Specimens ahied to 



