AND DESCRIPTIONS OF NEW SPECIES. 87 



My Cabinet. 

 Cabinet of Professor Vanuxem. 



Cabinet of P. H. Nicklin. 



Cabinet of R. E. Griffith, M.D. 



Cabinet of Academy of Natural Sciences. 



Diam. -3, Length -5, Breadth 1 inch. 



Shell subelliplical, transverse, thick ; substance of the shell thick ; 



beaks slightly prominent; ligament short; epidermis dark, and finely 



wrinkled ; rays green, hair-like, and undulating, particularly on the 



posterior half; cardinal tooth double, and deeply cleft in the left 



valve and single in the right ; lateral teeth short, straight, thick and 



enlarged towards the posterior end; posterior and anterior cicatrices both 



distinct, the smaller posterior one being placed directly over the larger 



and beneath the point of the lateral tooth ; dorsal cicatrices situated in 



the centre of the cavity of the beaks ; cavity of the beaks shallow and 



arched; cavity of the shell small arid irregularly undulated; nacre 



pearly white and iridescent. 



Remarks. — This little species first attracted my attention about 

 three years since, when I had seen but a single specimen. Although 

 a very small shell, I felt satisfied it possessed the characters of an 

 adult, and my curiosity being much excited in regard to it, I made 

 many efforts to obtain other individuals. For several of these I am 

 indebted to the kindness of Dr Hildreth of Marietta and to Mr Robert 

 Peter and J. S. Craft,'Esq. of Pittsburg. The fabalis most resembles 

 the parvus of Barnes. It has nearly the same size and outline ; but differs 

 much in the thickness of the valves and in the beaks. The fabalis is 

 covered with rays, the parvus has none. 



Unio Soleniformis. Plate X. fig. 17. 



Testa angusto-eUipticu, transversa, compressa, inaquilaterali, ad finem utrum- 

 que rotundatn ; valvulis tenuibus ; natibus prominulis ; valvula utraque tuber culum 



