68 



the hinge hne nearly flat with a sharp sulcus close to the margin. The 

 posterior and lower sides of this tubercle rise abruptly from the edge of 

 the valve. There is no sulcus along the margin in this part as there is in 

 B. Kloedeni. The median tubercle is a strongly elevated angular ridge 

 running from a point situated on the hinge line a little over one-fourth the 

 length from the posterior angle, downwards nearly to the ventral margin. 

 The anterior tubercle originates at a point situated on the hinge line a 

 little more than one-third the length from the anterior angle. It has a wider 

 base than the median tubercle, but is quite as angular along its crest. It is 

 abruptly elevated at the hinge Hne, but declines in height towards the ven- 

 tral margin just before reaching which it bends round and running along 

 the margin unites with the posterior tubercle. In front of it there is a deep 

 round sulcus with a sharp elevated ridge outside of it on the very edge of 

 the valve. This sulcus commences at the hinge line, and runs along the 

 anterior margin and nearly half the length of the ventral margin w^hen it 

 terminates abruptly. 



The left valve is like the right, but in the only good specimen observed 

 the posterior tubercle is more prominent. Length of the largest valve seen 

 IJ lines ; width near the posterior extremity 1 line. East Point, The Jum- 

 pers and other locahties in Divs. 3, 4, A. G. J. Richardson. 



B. VENUSTA, n. sp. — Carapace valves semi-ovate ; width a little more 

 than half the length ; posterior margin rounded, forming an obtuse angle 

 Avith the hinge line ; ventral margin moderately convex ; anterior extre- 

 mity somewhat narrower than the posterior, in the upper half straightish 

 and nearly at right angles to the hinge line, below rounded into the ventral 

 margin. There is an abruptly elevated rim all round except on the hinge 

 line and just within it a deep concave marginal sulcus which is partially 

 interrupted about the mid-length by a low vertical ridge which is scarcely 

 visible in some specimens. There are two large ridge like tubercles origin- 

 ating at the hinge-line and extending two-thirds the width across when they 

 converge and unite. They are separated by a deep conical sulcus. There 

 is a third obscurely developed ridge just behind the posterior tubercles 

 with which it unites below. The two principal tubercles divide the hinge 

 line into three nearly equal parts. When magnified thirty diameters the 

 surface is seen to be covered with minute rounded pits in some specimens 

 closely crowded together and in others separated, sometimes half their own 

 width. Length 1 line ; width about f of a hne. East Point, Chaloupe 

 River, the Jumpers and other places; Divs. 3, 4, A. G. J. Richardson. 



Genus Leperditia, Roualt, 



L. Anticostiana, Jones. The original specimen was from East Point, 

 but it occurs also at the Jumpers and other places !n Divs. 3, 4, A. G. 



