TRANSACTIONS OF WAGNER 



I04S 



TERTIARY FAUNA OF FLORIDA ^^ 



Macroma Gray, Ann. Phil., xxv., p. 136, 1825; P. Z. S., 1847, p. 186; err. typ. for 



Macoma Leach. 

 Psammobia (sp.) Turton, Dithyra Brit., p. 95, 1822; Teliina solidula Mtg. ; Lam., An. 



s. Vert., v., p. 514, 1818; Say, Journ. Acad. Nat. Sci. Phila., v., 219, 1827. 

 Psammotea Gray, P. Z. S., 1847. p. 186; not Turton, 1822, nor Lam. 

 Sangitinolaria (sp.) Conrad. Am. Mar. Conch., p. 34, 1831 ; Gould, Inv. Mass., p. 66, 



1841. 

 Rcxithccrus Conrad, in Tryon, Cat. Tell., p. 104, 1869; Macoma secta Conrad. 



Shell without lateral teeth, usually subtrigonal and with a marked posterior 

 flexure, the surface feebly sculptured concentrically or smooth; the siphons 

 naked. Type M. tenera Leach {= Teliina calcarea Gmelin). 



Subgenus Macoma s. s. Shell subtrigonal, the periostracum conspicuous ; 

 usually colorless, or, if colored, without a color pattern; flexure well marked; 

 the pallial sinus coalescent with the pallial line below and often discrepant in 

 the two valves ; inhabiting the cooler seas and especially boreal waters. 



Section Macalia Adams. Shell rounded, with a wide hinge-plate and ex- 

 ceptionally large teeth. Subtropical. 



Section Rexithcsrus Conrad. Shell large, inequivalve, with a smooth sur- 

 face, a large and strong deep-set ligament, behind which the dorsal margin is 

 conspicuously produced upward. 



Subgenus Psammacouia Dall, 1900. Valves equal, produced anteriorly, 

 bluntly truncate and hardly flexed posteriorly, with a smooth surface and in- 

 conspicuous periostracum. Tropical waters. Type Teliina Candida (Lam.) 

 Bertin {^T. galathea Hanley, Reeve). 



This group by its elongated Tagelus-like form, its delicate, often radially 

 hirsute, periostracum, and its habitat in the warmer seas where it replaces 

 the Arctic type of Macoma, is easily separable from the latter. The pallial 

 sinus is usually about half free instead of wholly coalescent below, as more 

 usual in typical Macoma. 



Section Psamniacoma s. s. Type T. Candida Bertin. Shell elongate, liga- 

 ment and resilium slender and wholly external. 



Section Psammotreta Dall, 1900. 



Like Psammacoma but shorter, with the resilium internal, shorter than 

 and partly separated from the ligament. Type Macoma aurora Hanley. 



This section bears to Psamniacoma the same relation that Scrobiculina 

 does to Angtilns in the genus Teliina. 



