AST. 6 NEW FRESH-WATER MUSSELS MARSHALL 6 



the Republic of Colombia, and A. dalyi E. A. Smith of India. The 

 widely separated habitats of the two species leads one to suspect that 

 when the anatomy of Acostaea lohata becomes known it may differ in 

 important respects from that of A. dalyi and cause the latter to be 

 placed in another genus. The anatomy of A. dalyi is known, but 

 until the anatomy of A. lohata becomes known dalyi must rest in the 

 genus Acostaea, for wide geographic separation, while usually indica- 

 tive of lack of close relationship, is not a taxonomic character. 



Another instance of resemblance between shells of these two widely 

 separated regions, is in the equilaterally triangular sinulus of South 

 American Anodonta-like fresh-water mussels which is duplicated in 

 Anodonta-like shells of the genus Pilsbryoconcha of Siam, Cambodia, 

 Sumatra, and Java. They belong to different families, the former to 

 the Mutelidae and the latter to the Unionidae. 



The reason for the abrupt downward bending of the anterior end of 

 Mycetopodella and Solenaia is unkown. Probably it has something to 

 do with enabling the mollusk to make a firm anchorage in the bottom 

 of streams. It calls to mind the anterior end of the genus Bartlettia 

 of the family Aetheriidae which is specialized for anchoring purposes. 



ANODONTITES GUANARENSIS, new species 



Plate 1, figs. 4-6 



Shell rather thin, somewhat compressed, outline nearly oval, 

 rounded and narrower in front, bluntly pointed and subtruncate at 

 the rear. Dorsal line nearly straight and making an obtuse angle 

 with the posterior margin. Ventral line curved, slightly swollen 

 just behind the middle, regularly rounding into the anterior margin, 

 which in turn rounds into the dorsal margin. The ventral and 

 dorsal margins form a blunt point just below the middle of the pos- 

 terior margin. Posterior ridge low and regularly rounded, but em- 

 phasized by a broad fuscous stripe radiating from the beak; the pos- 

 terior area with two similar but narrower fuscous rays. Anterior to 

 the posterior ridge the periostracum is smoothish but with indis- 

 tinct radiating striae. Anterior half of the shell polished and with 

 a number of radiating lines of rufflings. Posterior portion plentifully 

 covered with low periostracal laminae. Microscopic sculpture of 

 fine radiating striae commonly found in shells of the Mutelidae. 

 Color ashy to brownish olive, the concentric growth lines darker; 

 interior bluish white, highly iridescent around the margin and with 

 iridescent radiating fine lines. Prismatic edging rather broad, pallial 

 line about 5.6 millimeters from the margin. 



The type. Cat. No. 365225, U.S.N.M., measures: Length 54 mm.; 

 height, 30 mm.; diameter, 16 mm. It and a paratype, Cat. No. 

 365226, U.S.N.M., were presented by Dr. Henry Pittier, who collected 

 them in a dried lagoon at Mata Verde, near Guanare. Portuguesa. 



