BELEMNITES OF THE LIAS. 



79 



Belemnites Voltzii, 11. s. PI. XVII, fig. 43. 



Reference. Belemnites comjjressus, Voltz, var. b and c, ' Belemn.,' p. 53, pi. v, figs. 1 



and 2, 1830. 



Guard. Conoidal, compressed, smooth, with a central blunt or eroded termination 

 (when old). Two dorso-lateral fun-ows proceed along half the space of the apicial region, 

 and from the termination about ten small plaits extend to half the length of the furrows. 

 No ventral sulcus. 



Transverse sections show at the alveolar apex a regularly oval contour, the innermost 

 layers of the guard undulated by the dorso-lateral furrows. 



Longitudinal sections show the axis to be exceutric, most so at the alveolar apex, 

 from which it is reflected toward the back, and then continues subcentral to the end. 

 The inner and younger laminae end bluntly in arches, so as to indicate the young forms 

 to have been obtuse at the termination (Voltz made this remark, page 55 of his work). 



Greatest length observed, 5 inches, the diameter at the extremity being 1*2 inch. 



Proportions. Taking the diameter fi-om back to front at the alveolar apex at 100, 

 the cross diameter is about 90, the ventral radius 40, the dorsal 60. The axis in 

 variety b, Voltz (shorter and smaller variety), is 250; in the longer and larger variety, 

 c, 350. 



Phragmocone. Nearly straight in var. b, slightly arched in var. c ; in var. b the dorsal 

 region occupies one sixth of the circumference, in var. c one fourth ; in b the hyperbolar 

 regions occupy the twelfth of the circumference, in c one eighth. In var. c, along the 

 band which separates the hyperbolar from the ventral region occur small striae, which 

 cross the hyperbolic arcs. Of these Voltz says he could give no explanation. (See 

 B. inornatus.) 



Locality. I am not sure that specimens exactly corresponding with this description, 

 and constantly deficient of the ventral sidcus, have come under my notice from any 

 locality in England. One cause of this doubt is the uncertainty about the younger forms; 

 for while Voltz infers, from longitudinal sections, that the apex was always blunt in 

 var. B, and that in var. c it became blunt with age, we find Quenstedt referring to 

 figures of the young which are quite acute, with a very deep alveolus and very short axis 

 (' Cephalopoden,' p, 422, pi. xxvii, figs. 13, 17). But as he speaks also of the early 

 appearance of the dorsal furrows and of the later appearance of the ventral furrows, 

 "which sometimes become extraordinarily deep," it would seem to be the form here 

 called ventralis which he is describing. 



On the Scars at Whitby and Saltwick are many Belemnites which might be thought 



