120 OBSERVATIONS ON NAIADES, 



front of the umbonial slope; valves thick; rays hair-like; cardinal teeth large; lateral 

 teeth rather short and slightly curved; nacre pearly white and iridescent. 



Hab. Ohio river, near Cincinnati, Mrs Febiger. 



My Cabinet. 

 Diam. 1'2, Length 1'8, Breadth 1-8 inches. 



Shell subtriangular, angular behind and rounded before, ventricose ; 

 longitudinally furrowed in front of the umbonial slope, the furrow- 

 causing a slight emargination in the basal margin ; umbonial slope flat- 

 tened on the ridge ; substance of the shell thick ; beaks prominent and 

 rounded at the tip ; ligament short and thick ; epidermis yellowish- 

 brown and wrinkled ; rays numerous and hair-like ; cardinal tooth large, 

 elevated and deeply cleft in the left valve, single and emerging from a 

 pit in the right valve ; lateral teeth short and slightly curved ; anterior 

 cicatrices distinct ; posterior cicatrices confluent ; dorsal cicatrices 

 situated on the under part of the cardinal tooth ; cavity of the beaks 

 wide and rounded ; nacre pearly white and iridescent. 



Remarks. — This shell has recently come into my possession and was 

 taken near Cincinnati. It is different from any species I have seen, 

 and somewhat resembles the U. sulcatus (Nobis), having a furrow from 

 the beaks to the margin anterior to the umbonial slope. It differs 

 from it, however, in being more elongated and in being destitute of a 

 purple nacre. The disposition to flatness in the umbonial slope is re- 

 markable in this species. 



MEI.ANIA Elongata. Plate XV. fig. 29. 



TestA elevata et acute turritd, fusco-corned, purpureo-fasciata; anfractibus circi- 

 ter decern parum depressis; basi angulatd; apertura cosruleo-albd, longitudinis testa 

 quadrantem habente. 



Shell elevated and acutely turrited, dark horn colour with purple bands; apex 

 acute; whirls about' ten and slightly depressed; base angulated; aperture bluish- 

 white and about one fourth the length of the shell. 



