130 PROCEEDINGS OF THE ACADEMY OF 



DESCRIPTIONS OF NEW SPECIES OF MARINE BIVALVE MOLLUSCA. 

 BY GEORGE W. TRYON, JR. 



1. Crassatella Adeline, Tryon. Plate 6, fig. 1. 



Shell ovate, triangular, anteriorly rounded, posteriorly pro- 

 duced ; umbones depressed, slightly undulated. Surface white 

 with brown rays, occasionally marked with cuneiform characters 

 of darker color under a thin dark brown epidermis; within choco- 

 late color, margins white without crenulations. 



Length 3, alt. 2.25, diam. 1.13 inches. 



Habitat, unknown. Museum of the Academy. 



This species is nearly allied to G. Antillarum, Reeve, but is 

 not so gibbous, and is more narrowly produced behind; it is also 

 readily distinguished by its peculiar colored markings. 



2. Lucina (Codakia) Distinguenda, Tryon. Plate 6, fig. 3. 



Shell orbicular, depressed, disk-like, covered with flattened 

 radiating ridges which are crossed by numerous close-set, raised, 

 concentric striae. White with a faint tinge of pink : interior with 

 a broad marginal band of deep pink. 



Long. 3, alt. 2.G5, diam. 1 inches. 



Habitat., Gulf of California. W. M. Gabb. Museum of the 

 Academy. 



This fine large species has been confounded, by Mr. P. P. 

 Carpenter and others, with an analogous West Indian species 

 Lucina tigrina, Linn. It is readily distinguished, however, by 

 its flattened form and border, and more depressed ribs. 



3. Circe (Crista) bidivavicata, Tryon. Plate 6, fig. 2. 



Shell oblong-oval, thick, somewhat ventricose, sides declining 

 convexly and ventral margin slightly rounded, covered b} T radiating 

 rounded ribs which are finally bifurcate and nodose ; ribs poste- 

 riorly bi-divaricate, forming a series of M's. Rust colored with 

 brown splotches, white within. 



Long. 1.65, alt. 1, diam. .65 inch. 



Habitat. Red Sea. Museum of the Academy. 



This species resembles Crista divaricata, Chemn., its charac- 

 teristic difference being the doubly divaricate disposition of its 

 ribs. 



