292 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.xxiii. 



Genus METIS H. and A. Adams, 1856. 



Type, Tellina meyeri Dunker. 



Capsa Lamarck, 1799, not Humphrey, 1797; Casjxi Bosc, 1802; 

 Lutricola Carpenter, 1863, not Bluinville, 1825. 



Genus GASTRANA Schumacher, 1817. 



Type, TeUliia fragtllx Linnanis. 



Frag ilia Deshayes, 1848; Diodonta Deshayes, 18'16, not Schu- 

 macher, 1817. 



Genus MACOMA Leach. 



Subg-enus Macoma Loach, 1819. Type, Macoma tenera Leach 

 {= Tellina calcarea Gmelin). 



Valves subtrigonal, rarely inflated, subequilateral, with a well- 

 marked posterior flexure; sinus usually confluent below with the pal- 

 lial line. Tertiary to recent in the cooler seas. Macroma Gray, 1825, 

 and Limicola Leach, 1852, not Koch, 1816, are synonymous. 



Section Macalia H. Adams, 1860. Type, Tellina hruguierei 

 Hanley. 

 Tellinungula Roemer, 1872, and Capsa Trj^on, 1869, not Hum- 

 phrey, 1797, are synonyms. 



? Section Rexithiierus Conrad, 1869. Type, Macoma secta Conrad. 



Subgenus Cymatoica Dall, 1889. Type, Tellina xindidata Hanley 

 (+ occidentalis Dall). 



Subgenus Psammacoma Dall, 1900. Type, Psamnnotcea Candida 

 (Lamarck), Bertin. 



Valves elongate, convex, thin, the posterior end markedly shorter; 

 posterior flexure obsolete; sinus (in the type) free, or only partly coa- 

 lescent with the pallial line. Tertiary to recent; warmer seas. 



Section Psammacoma s. s. Sinus free, gibbous, short. Type, 

 Macoma Candida (Lamarck^), Bertin. 



Section Cydippina Dall, 1900. Sinus partly coalescent below, | 

 elongated. Tj^pe, Macoma hrevifrons Say. 



Section Psammotreta Dall, 1900. Type, Tellina aurora Hanley. 

 Like Pmmmacoma^ but shorter, with the resiliuin internal, shorter 

 than and partly separated from the ligament. This section l)ears to 

 Psammacoma a relation similar to that which Scrobicidina does to 

 Angulus in the genus Tellina. 



^This is the Tellina galaihea Hanley, not Lamarck, according to Bertin, and the 

 Tellina sei'icina Jonas, 1844. 



