62 NEW UNIONIDiE, MELANID^, ETC., 



Shell smooth, oblique, inflated before, very inequilateral, acutely angular and 

 attenuate behind, rounded before ; substance of the shell somewhat thick, slightly 

 thicker before ; beaks swollen and nearly terminal ; ligament long, rather thin and 

 brown; epidermis rather dark olive, with indistinct rays over nearly the whole 

 disk, usually with two broad, distant, yellowish bands marking the lines of growth ; 

 umbonial slope obtusely angular and very oblique ; posterior slope very narrow, dark 

 green, with two indistinct raised lines on each valve from the beaks to the margin ; 

 cardinal teeth long, lamellar, very oblique, corrugate, single in the left and double in 

 the right valve ; lateral teeth very long, oblique, lamellar and corrugate ; anterior 

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

 and very slightly impressed ; dorsal cicatrices small and placed above the centre of 

 the cavity of the beaks ; cavity of the shell deep ; cavity of the beaks rather deep 

 and wide ; nacre white or bluish, very rich and very iridescent. 



Remarhs. — I have three specimens of this interesting species before me. It was 

 first called to my attention by Don P. M. Paz, who procured several specimens in 

 Europe and brought them, kindly, to this country, to submit to me. I have great 

 pleasure in giving it the name of that zealous zoologist. Subsequently Dr. Hartman 

 submitted some specimens to me. To both these gentlemen I am indebted for 

 specimens of this very interesting species. All those which I have seen are more or 

 less worn at the tips of the beaks, and therefore the characters of the undulations, if 

 there be any, cannot be described. In one of the specimens there is a slight appear- 

 ance of transverse undulations. The beaks are nearly terminal, and the swelling is 

 enlarged anteriorly over the disk. All these specimens have but three lines of 

 growth, which of course are very distant. They are broad, yellowish and very dis- 

 tinct. Two of the specimens have a rich satin-like pearly lustre ; the third is bluish 

 white, and not satin-like. It belongs to that group of oblique species which have 

 long, oblique cardinal teeth, sinrjle in the left and double in the right valve, of which 

 tumidulus, (nobis,) from Slam, may be considered the type. It may be at once dis- 

 tinguished from it by being a wider and thinner species, and having a darker and 

 smoother epidermis. It is very nearly of the same outline as Tigris, Per., from 

 Bagdad, but that is a much smaller species, with a brown polished epidermis, and 

 differs totally in the cardinal teeth, which in Tigris are not lamellar or oblique, but 

 double in the left valve. It is closely allied to Ingallsianus. (nobis,) but it is a larger 

 species, with more terminal beaks and much greater inflation of the anterior half of 

 the shell. It will be observed above that two habitats (China and Siam) are given. 

 I think it probable that they are from China only. 



