38 DESCRIPTION OF NEW 



Unio Ingallsianus. pi. XXIV. Fig. 41. 



Testa Isevi, transversa, inflata, cylindraced, postice acuto-angulatd, e natibus postice bilineatis ; valvulis 

 sublenuibus; natibus subprominentibus ; epidermide tenebroso-olivaced, striata; dentibtts cardinalibus prx- 

 longis, laminatis el in valvuld dexlrd solum dvpUcibus; lateralibus longis, laminatis, rectis; margaritd 

 cxruleo-albd et valde iridcscente. 



Shell smooth, transverse, inflated, cylindrical, acutely angular behind, with two lines posteriorly from the 

 beaks ; valves rather thin ; beaks rather prominent ; epidermis dark-olive, striate ; cardinal teeth very long, 

 lamelliform, straight and in the right valve only double ; lateral teeth long, lamelliform, straight ; nacre bluish- 

 white and very iridescent. 



Hab. Siam, Thomas R. Ingalls, M. D. 



My cabinet and cabinet of Dr. Ingalls. 

 Diam. .7, Length .8, Breadtli 1.9 inches. 



Shell smooth, very transverse, inflated, cylindrical, acutely angular behind, obtusely 

 rounded before, with two minute, slightly elevated lines running from the beaks towards 

 the posterior margin, on the posterior slope flattened, near the basal margin slightly com- 

 pressed; substance of the shell rather thin; beaks rather prominent, submedial; ligament 

 short and rather thick; epidermis dark-olive, dull, striate over the whole disk, without rays; 

 umbonial slope obtusely angular; cardinal teeth very long, lamelliform, straight, and in 

 the right valve only, double; lateral teeth long, lamelliform, straight and double in the left 

 valve; anterior cicatrices confluent; posterior cicatrices confluent; dorsal cicatrices placed 

 on the plate immediately over the centre of the cavity of the beaks; cavity of the shell 

 deep and rounded; cavity of the beaks rather shallow and rounded; nacre bluish-white, 

 pearly and iridescent. 



Remarks. — This very interesting shell was sent to me by Dr. Ingalls, of Greenwich, N. Y. 

 It was the only new one among several he received from Siam. To his kindness for this 

 and other species, I am indebted, and I dedicate it to him. The form is very unusual, and 

 assimilates to the U. Cail/audil, Fer., from Egypt. The colour is of the same dull olive. 

 It may be distinguished in the e.\terior by its being less cylindrical and more angular 

 behind; and in the interior, by the peculiar form of the cardinal teeth, which are long and 

 lamelliform and double in the right valve, while in the Caillaudii they are short, erect, and 

 double in the left valve. The beaks are also much more medial. The nacre is of an 

 uncommonly fine pearly character, and in this specimen it is delicately striate from the 

 cavity of the beaks towards the margin. In the description, it may be observed that I 

 have stated the anterior cicatrices to be confluent, a rather unusual character in the 

 Uniotics. Of the smaller under cicatrix there is no appearance in this specimen, but it 

 may be embraced in the large one. There is, however, a very distinct cicatrix above the 

 large one. It is much to be regretted that the soft parts were not preserved, as the 

 peculiar cardinal teeth and muscular cicatrices indicate a different disposition of the mus- 

 cular fibres of the adductor and retractor muscles. The enlargement on the posterior 

 portion of the disk towards the basal margin, indicates the female character of this 

 .specimen. 



