254 CARBONIFEROUS LIMESTONE BRACHIOPODA. 



twelve on each side at seven or eight lines from the beak, be- 

 yond which they are either simple, or more frequently di- or 

 tri-chotomous as they approach the margin, more rugged and 

 irregular in direction than those of the entering valve, varying 

 from three to six in three lines at 1 inch from the beak ac- 

 cording to the amount of bifurcation. Internal mesial sep- 

 tum of receiving valve very long, reaching nearly to the 

 front margin, the lines of growth slightly arched towards 

 the beak ; rostral divaricating portions scarcely two-thirds the 

 length of the combined mesial portion, but of slightly greater 

 width : two mesial septa of entering valve narrow, scarcely 

 one-third the depth of the mesial septum of the receiving 

 valve; anterior broad ends very obliquely truncated, but 

 reaching rather less than half the length of the valve. 

 Average width 1 inch 2 lines, proportional length of enter- 

 ing valve y^Q, length of hinge-line -^■^■^, length of re- 

 ceiving valve varying from -f^^Q to |^g, height of cardinal area 

 varying from ^^^ in the former to y^^''^ in the latter, width of 

 mesial ridge and sinus in the front margin y^^^^, depth of en- 

 tering valve 3%^Q to y^^Q, depth of receiving valve y^^^^ to y^^^^ . 



Some of the specimens of this species so nearly resemble 

 Spirifers, that it was not until I made sections in various direc- 

 tions of several specimens, demonstrating the invariable presence 

 of the two narrow longitudinal subparallel septa in the entering 

 valve, and the wide, extremely long mesial septum in the re- 

 ceiving one, with its internal divaricating portions flanking the 

 triangular opening in the cardinal area, perfectly agreeing with 

 Pentamerus, as well as the absence of spiral appendages, that I 

 was convinced of its true genus. I have had the pleasure of de- 

 monstrating these specimens to M. de Verneuil, who, like myself, 

 was fully satisfied of their being true Pentamerij and saw in them 

 the first example of the genus in carboniferous rocks (the Pen- 

 tamerus Sella and P. plicatus of Kutorga being obviously Came- 

 rophoria). 



Not very uncommon in the impure lower carboniferous lime- 

 stone of Kendal, Westmoreland. 



[Col, University of Cambridge.) 



Leptaena [Chonetes) polita (M^Coy). 



Desc. Transversely fusiform ; hinge-line exceeding the width of 

 the shell, forming narrow semicylindrical convoluted ears, each 

 bearing four or five small spines; receiving valve nearly hemi- 

 spherical, very gibbous in the middle and towards the beak, 

 which is large, inflated, and seems considerably to overhang 



