CHIEFLY OF THE UNITED STATES. 283 



prominent, minutely and closelj' plicate; epidermis reddish-brown, without rays, 

 shining; cardinal teeth somewhat compressed, oblique, crenulate, slightly double in 

 both valves ; lateral teeth long and somewhat curved ; nacre white and iridescent, 

 Proc. Acad. Nat. Sci. 1865, p. 76. 

 jg^aJ. — Don Patricio Maria Paz. 



Cabinet of Don P. M. Paz, Madrid. 

 Diam. -7, Length 1-2, Breadth 17 inch. 



Shell plicate, subquadrate, slightly sulcate, sublenticular, inequilateral, rounded 

 behind and round before ; substance of the shell somewhat thick, thicker before ; 

 beaks slightly prominent, minutely and closely plicate, almost granulate ; ligament 

 long, thin and dark brown; epidermis reddish-brown, without rays, shining, with 

 distant marks of growth; umbonial slope very slightly raised and rounded; 

 posterior slope carinate, almost alate; cardinal teeth somewhat compressed, 

 crenulate,. double in the right and slightly double in the left valve ; lateral teeth 

 long, somewhat curved and corrugate ; anterior cicatrices distinct and well im- 

 pressed ; posterior cicatrices confluent and slightly impressed ; dorsal cicatrices 

 placed in the centre of the cavity of the beaks ; cavity of the shell shallow and wide ; 

 cavity of the beaks very shallow and rounded ; nacre white and iridescent. 



Remarlcs. — A single specimen only is before me. Its habitat is unknown, but it is 

 probably from South America. The epidermis and minute folds are very much like 

 elllpticus (nobis) from Brazil. While in these characters it closely resembles 

 ellipticiir'i, the outline of the shell is entirely different, being quadrate, more inflated 

 and having a carina almost amounting to a wing. While ritfofuscus belongs to the 

 quadrate division, elllpticus belongs to the wide group. The beaks of the specimen 

 being eroded for some distance, their character cannot be described, but I suspect 

 that the small folds, which reach one-third down the side, will be found in perfect 

 specimens to decrease to the apex. 



Unio Wrightil* pi. 39, fig. 97. 



Testa plicata, lata, ad umbones inflata, valde inoequilaterali, postice acuto-angulata, antice rotundata ; 

 valvulis crassiusculis, antice crassioribus ; natibus subpromiuentibus et crebre plicatis ; epider- 



* " In a paper on ' Chinese Shells,' by Dr. Baird and Mr. H. Adams, published in the Proceedings of the 

 Zoological Society of London, May 9th, 1867, there are some remarks and claims which call upon me for 

 correction. 



"1st, ' Unto Douglasice.' It is stated that 'in 1833 Dr. Gray shortly described and accurately figured in 

 the 12th volume of Griffith's edition of Cuvier a species of JJnio, which he called U. Doiiglasue,' &c. Further, 

 that ' Mr. Lea, some years afterwards, from notlcnowing the shell as figured in Griffith, described and figured 

 a species from China, which he named U. Murchisomanus, but which there is no doubt is the same as U. 

 Douglasice of Gray.' In the above statements there are several to which I beg leave to demur. It is 



70 



