34 NEW UNIONID^, MELANID^, ETC., 



cavity of the beaks rather shallow and angular; nacre salmon colored, paler towards 

 the margin and iridescent. 



RemarTcs. — A single specimen only is before me. In outline it is nearly allied to 

 Kirkii, herein described, but it has more folds, two-thirds of the disk being covered 

 with small ones, which come in regular rows from the anterior and posterior portions, 

 and form on the sides irregular and zig-zag corrugations. It differs from Kirhii in 

 color, folds, rays and the teeth. The nacre of this specimen is salmon in the 

 cavities, but whitish towards the margin. Other specimens may prove to be white, 

 and others again of a darker salmon. It is not likely that any will be found pink or 

 purple. This specimen reminds one somewhat of apiculatis, Say, but that is larger? 

 more square, and has rough nodules over the whole disk, while this has small 

 interrupted folds which border on granulations. The last remark may also be applied 

 to Aferulus, herein described. 



Ukio Aferulus. PL 13, fig. 34. 



Testa valde plicata, obliqua, subcompressa, valde insBquilaterali, antice rotunda, postice subbiaugulata ; 

 valvulis crassiusculis, antice crassioribus ; natibus subprominentibus, solidis, ad apices undulatis ; epi- 

 dermide luteo-cornea ; dentibus cardinalibus parviusculis, sulcatis ; lateralibus subrcctis, curtis, in 

 utroque valvule duplicibus ; margarita dilute sulmonis colore tincta et valde iridescente. 



Shell much folded, oblique, somewhat compressed, very inequilateral, round before, 

 somewhat biangular behind ; valves somewhat thick, thicker before ; beaks somewhat 

 prominent, solid, undulate at the tips; epidermis yellowish horn color; cardinal 

 teeth rather small and sulcate ; lateral teeth nearly straight, short and double in 

 both valves ; nacre pale salmon color and very iridescent. 

 Proc. Acad. Nat. Sci., 1864, p. 109. 



Hah. — Lake Nyassa, Central Africa, John Kirk, M. D., of the Zambezi Expedi- 

 tion. 



My cabinet. 

 Diam. -5, Length -8, Breadth 1-1 inches. 



Shell very much folded, oblique, somewhat compressed, very inequilateral, round 

 before and somewhat biangular behind ; substance of the shell somewhat thick, 

 thicker before; beaks somewhat prominent, solid and undulate at the tips; liga- 

 ment rather short and light brown ; epidermis yellowish horn color, with two dis- 

 tant marks of growth ; umbonial slope slightly raised and obtusely angular ; posterior 

 slope narrow elliptical, with one dark impressed line on each valve from the beak to 

 the posterior basal margin ; cardinal teeth rather small and sulcate ; lateral teeth 

 nearly straight, short and double in both valves ; anterior cicatrices distinct, rather 

 small and well impressed ; posterior cicatrices confluent, large and moderately 

 impressed ; dorsal cicatrices placed immediately over the centre of the cavity of the 



