NEW PEARLY FRESH-WATER MUSSELS FROM MEXICO 



AND URUGUAY. 



By William B. Marshall, 

 Aagistant Curator, Division of Mollusks, United States Natiotial Museum. 



Among a lot of material recently received for determination from 

 Dr. Florentino Felippone, of Montevideo, Uruguay, and from Dr. 

 A. L. Herrera, Director of Estudios Biologicos, City of Mexico, 

 Mexico, were three new species which are herein described. 



elliptic HERRERAE. new species. 



Plate 1, figs. 6-8 ; plate 2, figs. 4, 5 ; plate 3. 



Shell inflated, strong, moderately heavy; outline nearly elliptical, 

 very slightly narrower in front, dorsal margin liglitly arched, with 

 a small elongate lunule in front of beaks, ventral margin rounded; 

 nepionic shell with several indistinct concentric raised lines but 

 without granules ; later the young shell develops a number of slightly 

 elongated granules arranged in quincunx order, and the upper part 

 of the posterior dorsal area has a number of curving raised lines 

 running from the posterior ridge to the margin; periostracum 

 smooth, unctuous, slightly glossy, closelj^ applied, and witli no 

 tendency to peel; color pale at the tips of the beaks, then deep 

 green, changing farther down to light chestnut, nearly the whole 

 shell plentifully rayed with darker green, even the very young shell 

 showing these green rays. Nacre silvery white, very iridescent pos- 

 teriorly, thicker in front; pallial line well marked, much crinkled; 

 anterior adductor scars deep, clifflike at the upper part, the bottoms 

 with roughened steplike thickenings; posterior adductor scars well 

 marked, fairly deep at upper part; pseudocardinal teeth very rough 

 and grooved and not distinctly divided into two parts in each valve; 

 lateral tooth of left valve long, a little spatulate, sliglitly granular, 

 obliquely grooved lengthwise; laterals of left valve two, the inner 

 one larger and much like the lateral of the right valve, prismatic 

 margin very narrow, not over a millimeter wid*e at the widest p«rt, 

 its color grayish-ashy. 



Type.— C^t. No. 347183, U.S.N.M. It measures : Length. 71 nun. ; 

 height, 4.5 nmi. ; diameter, 32 mm. It comes from Estera del Avi- 

 leno, in the State of Tamaulipas, Mexico. It and another speci- 



No. 2485— Proceedings U. S. National Museum, Vol. 63. Art. 16. 



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