45 



carinated along the middle, somewhat concave towards the sides ; umbo 

 laterally compressed ; beak small, strongly incurved over the umbo of the 

 dorsal valve but apparently not in contact therewith. There is a small 

 sinus in this valve with a prominent ridge on each side which produces a 

 doubly carinated aspect. The dorsal valve is more broadly and uniformly 

 convex than the ventral with a shallow sinus, in the middle of which is a 

 narrow mesial fold. Surface with from twenty to twenty-five small -obscure 

 radiating ribs which occur also on the carinse of the ventral valve and the 

 small fold in the sinus of the dorsal valve. Length about 3 lines ; width 

 about 3i lines. This species is evidently congeneric with R ? recurvirostra, 

 Hall. The Jumpers ; Div. 4, A. G. J. Richardson. 



Genus Camerella, Billings. 



C. B.EYER§A,=zPentamerus reversus, B. Rep. 1857, p. 295. — Junction 

 Cliir;Div. 1, A. G. 



C. Ops, B., Pal. Foss., vol. i, p. 148.— The Jumpers ; Div. 4, A. G. 



C. LENTicuLARis, n. sp. — Shell ovate, lenticular, both valves about 

 equally convex ; sides and front rounded ; greatest width a httle above the 

 mid-length ; beaks about equal, closely incurved. On one valve there 

 is an obscure mesial fold and on the other a sinus. Most of the specimens 

 have a few obscure ribs half a line wide, but these are sometimes so slight- 

 ly developed that the shell seems to have an even surface all over with the 

 exception of the fold and sinus which are always more or less conspicuous. 

 When the surface is very perfectly preserved fine concentric striae are visi- 

 ble. Width of a specimen of the ordinary size 9 fines ; length 8 lines ; 

 depth of both valves 4 lines. Reef Point ; Div. 1, A. G. J. Richard- 

 son. 



This species differs from 0. reversa in its regularly lenticular form and 



less gibbosity. It appears in the same group of strata, but at a higher 



level. 



Genus Pentamerus, Sowerby. 



P. Barrandei, B., Rep. 1857, p. 296. — Becscie River Bay ; Div. 2, 

 A. G. 



P. OBLONGUS, Sowerby. — South-west Point, South Point, Cormorant 

 Point, East Point and the Jumpers ; Divs. 3, 4, A. G. 



Genus Stricklandinia, Billings. 



S. LENS, Sowerby. — East of Jupiter River, South-west Point and The 

 Jumpers ; Divs. 3, 4, A. G. 



S. lirata, Sowerby. — East Pomt, South-west Point, Heath Point and 

 The Jumpers ; Divs. 3, 4, A. G. 



