378 AXEL A. OLSSON 



15. Shell broadly subovate in shape, growth-line sculpture coarsely 

 wrinkled. 



Genus Florimetis 



f. Posterior flexure smaller, the posterior area itself narrow, not expanded 

 or winged. 



fa. Ligament entirely external, slender, attached to a narrow scar; no 

 nymphal ridge. 



16. Like Macovia, s.s. in shape, subovate, the posterior side short. Caribbean. 



Genus Austromacoma 



fb. Ligament partly internal, the resilifer scar short, triangular in shape, 

 immersed in the hinge plate and pressed against the cardinal tooth. 



17. Shell elongate, tellinoid or tagelloid, the posterior side much shorter 

 than the anterior, usually weakly flexed. 



Genus Psammaco'ma 



18. Shell elongate, tellinoid or subtriangular, generally flexed, the posterior 

 side narrowly rounded or truncated at the end. 



Genus Psammotreta 



19. Shell in shape like Sanguinolaria, depressed, the flexure weak or absent, 

 the posterior-dorsal area small, the end pointed. 



Genus Ardeamya 

 Db. The adductor scars nearly equal in size, 



g. Surface marked with strong, wavelike undulations. 



20. Shell small, lediform, its posterior end strongly flexed. 



Genus Cymatoica 

 h. Surface smooth or with the usual concentric lines. 



21. Shell in shape like Psammobia (Gobraeus), oblong, subquadrate, equi- 

 valve, the posterior side wide, and not flexed. Surface smooth and 

 usually marked with obliquely trending, incised lines across the middle 

 and anterior portions of the disk. 



Genus Psammothalia 



Subfamily TELimiNAE 



Shell narrowly or broadly lanceolate to ovate in shape, the posterior 

 side generally shorter and often strongly flexed towards the right, hence, the 

 valves are usually unequal, the left one larger and more convex, the right 

 often depressed across the middle. Hinge provided with both cardinal and 

 lateral teeth. Surface sculptured with concentrics, generally heavier on the 

 rostral areas. 



Genus TELLDfA Linn§, 1758 



Type species by subsequent selection, Lamarck, 1799, Tellina virgata 

 Linne. Indo-Pacific. 



Lamarck's citation of only one species as illustrating the characteristics 

 of each genus discussed in the Prodrome is considered a valid type designa- 

 tion.13 



Shell more or less elongate, the posterior side narrowed and produced, 

 flexed strongly to the right, and carrying a differentiated rostral area. 

 Surface sculptured with raised or rounded concentrics usually becoming 

 coarser and scabrous on the rostral area. Hinge fully formed; there are 

 two cardinal teeth in each valve, one of which is bifid with bordering sockets; 



"Olsson, A.A., Harbison, A., and others, 1953, Mon. Acad. Nat. Sci. Philadelphia, No. 

 8, p. 121. 



