﻿EXOTIC UNlUNIDvE. 255 



the posterior and anterior portions as well as along the basal margin. The folds being- 

 well pronounced, cause them to be observed on the interior, and soften the nacre, which 

 has a beautiful satin-like appearance. The successive folds on the tip form a beautiful 

 line of acute angles on the middle. 



Unio persulcatus. PI. 40, fig. 135. 



Testa crebre sulcata, oblonga, vald£ insequilaterali, compressa, postiee subangulata ; valvulis subcrassis ; 

 natibus prominulis ; epidermide virido-fusca, radiis capillaris ; dentibus cardinalibus magnis, sulcatis 

 crenulatisque ; lateralibus sublongis rectisque ; margarita, purpurea et valde iridescente. 



Shell closely sulcate, oblong, very inequilateral, compressed, subangular behind ; 

 valves rather thick ; beaks somewhat prominent ; epidermis greenish brown, with 

 numerous hair-like rays ; cardinal teeth large, sulcate and crenulate ; lateral teeth 

 rather long and straight; na,cre purple and very iridescent. 



Unio persulcatus, Lea. Proc. Acad. Nat. Sci., 1859, p. 153. 



Hdb. — Mexico. Prof. Hanley. 



Cabinet of Prof. Hanley. 

 Diam. -6, Length 1*1, Breadth 2 inches. 



Shell closely and minutely sulcate, oblong, very inequilateral, compressed, sub- 

 angular behind, slightly curved at the base ; substance of the shell rather thick ; 

 beaks somewhat prominent, nearly terminal ; ligament rather short and thin ; 

 epidermis greenish brown, with numerous hair-like rays over the disk, but more 

 distinctly marked on the posterior slope, where there is a yellow band from beak to 

 margin; umbonial slope slightly raised into an obtuse angle; posterior slope com- 

 pressed and raised into a sharp keel ; cardinal teeth large, sulcate and crenulate ; 

 lateral teeth rather long and straight ; anterior cicatrices distinct and well impressed ; 

 posterior cicatrices distinct ; dorsal cicatrices numerous, well impressed and extending 

 from the centre of the cavity along the base of the cardinal tooth ; cavity of the shell 

 very shallow ; cavity of the beaks shallow and subangular ; nacre rather dark purple 

 very and iridescent. 



Remarks. — A single specimen only of this remarkable species was submitted to me 

 by Prof. Hanley. It simply has the habitat " Mexico " upon it. The most promi- 

 nent character, which strikes the observer at once, is the closely set, transverse, 

 parallel furrows which cover the whole disk and probably reach to the tips of the 

 beaks, which, unfortunately, in this specimen are eroded. The yellow band on each 

 valve, reaching from the beaks to the posterior dorsal margin is very unusual. The 

 purple nacre is very fine and in some lights gives a copper color. In outline it has a 

 very close affinity to some of our various forms of complanatus. The capillary rays 

 on the posterior slope are very beautiful and well defined. 



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