88 INVERTEBRATA. 



pressed by a dorsal flattening; it expands slightly at the proximal 

 end : distal end submucronate, mucro short and stout. No furrows. 



The Surface is completely covered with ridges and striae, some 

 of the former corresponding in position with the structural radii 

 seen in transverse section : the striae are smaller, and much more 

 numerous (about 10 striae to 1 mm.). 



The proximal end shews a shallow cavity much like the calyx 

 of a coral, the constituent radii standing out clearly in pencil-groups 

 suggestive of coral septa. The expanding of the guard at this 

 region shews that this proximal cavity was at, or near to, the alveo- 

 lar cavity, but it obviously is not simply that cavity itself but is 

 the result of destroying agents acting upon original peculiarities of 

 structure. Whereas in Actinocamax we have a group of Belemnites 

 with the outer layers more and more friable in the neighbourhood 

 of the phragmocone, here the contrary seems to be the case, so 

 that a hollowing out of the upper end of the Belemnite has 

 occurred. 



A transverse section shews the contour to be nearly circular, 

 rendered somewhat irregular by the slight dorsal flattening. The 

 characteristic exogenous structure is well seen, with few and strong 

 growth circles and unusually well-marked radii. These radii 

 converge to the centre, most of them being continuous so that 

 the rays become numerous and closely packed towards the cen- 

 tre, but as the more central part is approached they become 

 irregular, curving, and wavy, converging towards and uniting with 

 one another in a manner recalling the section of a Palaeozoic 

 cyatliophyllum. In ordinary Belemnites the radii run straight 

 to the centre — (Compare Fig. in Phillips's British Belemnites, Pal. 

 Soc, p. 14). 



The axis of the guard is subcentral. Phragmocone unknown. 



Measurements. Length, 23 mm. ; breadth near middle, 7^- mm. ; 

 lateral diam. at proximal end, 8 mm. ; dorso-ventral diam. at 

 proximal end, 8 mm.; dorso-ventral diam. at middle, 7 J mm. The 

 axial line meets the diameter excentrically, so as to mark off radii 

 of 3 mm. and 4 mm. respectively. 



Affinities and Differences. Belemnites Upivarensis is well 

 separated from all other species by the ornamented character of 

 its whole surface. I believe these surface striae to be the true sur- 



