44 



specimens, of a greyish silvery lustre like that of Atrypa reticularis. Only- 

 two specimens were collected. The largest of these is 7 lines in width and 6 

 lines in length ; depth of both valves 5 lines. The other is 5 lines in length 

 and Si in width ; depth of both valves 4 lines. 



From the peculiar character of the shell I am inclined to think that this 

 is not a true Rhynchonella. 



Challoupe Rivers ; Div. 4, A. G. J. Richardson. 



R. Pyrrha. — Shell ovate or nearly circular ; width usually a little grea- 

 ter than the length. Ventral valve rather strongly convex, most prominent 

 at one-third the length from the beak ; mesial sinus deep at the front mar- 

 gin and usually flat in the bottom, dying out on the umbo ; the latter with 

 a concave slope on each side to the cardinal angles and margin ; beak 

 small incurved but not in contact. Dorsal valve more uniformly convex 

 than the ventral, a prominent mesial fold which becomes a sulcus on the 

 umbo. There are about twenty ribs of which there are usually four in the 

 mesial sinus. Width 5 or 6 lines ; length a little less. One mile east of 

 Otter River; Div. 2, A. G. J. Richardson. 



R. viciNA, n. sp. — Shell ovate ; sides in the anterior two-thirds uni- 

 formly rounded ; above which they are somewhat straight and meet at the 

 beak at an angle of 110° ; front margin somewhat concave at the sinus. 

 Ventral valve moderately convex, most prominent at the upper third, some- 

 what flattened or concave on each side of the umbo ; the latter moderate ; 

 beak small rather closely incurved ; sinus concave, dying out on the umbo. 

 Dorsal valve moderately convex, the fold distinct but not abruptly elevated, 

 dying out at the upper third. There are twelve strong angular ribs on the 

 ventral valve, two of which, with a smaller one on the left side, are in 

 the sinus. The same number on the dorsal valve, three of them on the 

 fold. Length 6 lines ; width 7 lines. South-west Point ; Div. 4, A. G< 

 J. Richardson. 



A single specimen only was collected. 



R. Eva. — Shell small, ovate ; sides and front margin rounded ; apical 

 angle variable, from 90° to 120°. Ventral valve strongly convex along the 

 middle ; beak closely incurved : the sinus slightly developed. Along the 

 median line there are usually three strong ribs, diverging towards the 

 front, one of these in the sinus ; outside of these three there are four or five 

 smaller ones in each side. Dorsal valve somewhat broadly convex, a faint 

 mesial sinus on the umbo which towards the front becomes a shghtly elev- 

 ated mesial fold with two strong ribs. In very perfect specimens, the front 

 part is marked with fine zig-zag striae. Length about 3 fines ; width usually 

 a little greater than the length. East Point ; Div. 3, A. G. J. Richardson. 



R, MICA, n. sp.— Shell small, transversely ovate or sub-circular. Ventral 

 valve strongly convex, uniformly arched from beak to front, dichotomously 



