KXOTIC UNIOXIDi^Ii. 7jj 



the posterior and anterior portions as well as along the basal margin. The Iblds 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. 1.^)5. 



Testa crebre sulcata, oblonga, valde inasquilaterali, eomprcssa, postico subaiigulatfi ; valvulis subcrassis ; 

 natibus prominulis ; epidermide virido-fusca, radiis capillaris ; dentibus cardiualibus luagnis, Hulcatis 

 crenulatisque ; lateralibns sublnngis rfiotisfpio ; mar^arita purpurea ct vald^ irideseente. 



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

 valves rather thick ; beaks somewhat prominent ; epidei'mis greenish brown, with 

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

 rather long and straight; nacre purple and very iridescent. 



I'liio po-suh-atus, Lea. Proc. Acad. Nat. Sci., 185!), p. 1.38. 



Hah. — Mexico. Prof. Hanley. 



Cabinet of Prof. Hanley. 

 Diam. -6, Length 11. 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, unfortunatel}', in this specimen are eroded. The j-ellow 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 romplanatu-'^. The capillary rays 

 on till' posterior slope are very beautiful and well defined. 



