TRANSACTIONS OF WAGNER 

 1388 



TERTIARY FAUNA OF FLORIDA 



usually absent; the lunule small and deeply impressed, unequal in the valves, 

 as in many Lucinas, and larger in the right valve. The adductor scars are 

 Lucinoid, the internal margins crenulate, the shell more or less orbicular, and 

 generally rather convex. The species of the early Tertiary very often have 

 the internal margin of the valves entire and some of them by their form indi- 

 cate a transition towards the Lucinas. The following subdivisions may be 

 recognized : 



Section Divaricella s. s. 



Valves suborbicular, subglobose, the umbones inconspicuous, the dorsal 

 areas not indicated, the cardinals two in each valve, the ligament and resilium 

 united, deeply inset but not strictly internal, the excavated striae forming an 

 angle on a line radial from the beaks. Type D. ornata Reeve. Mauritius. 



Section Pompholigina Dall. 



Valves extremely tumid, the umbones subspiral, the anterior and posterior 

 dorsal areas indicated, the margins not crenulate ; otherwise as in the typical 

 section. Type Lucina gibba Gray. West Africa. 



Section Bourdotia Dall. 



Valves subcompressed, inequilateral, subquadrate, the anterior end pro- 

 duced, the anterior dorsal margin convexly arcuate, the internal margins plain, 

 a single minute cardinal in each valve, the laterals obsolete ; the excavated 

 external striae arcuate, not angulated. Type Lucina (Cyclas) Bourdoti Coss- 

 mann, Journ. de Conchyl., xxx., p. 115, pi. v., figs. 3 a-b, 1882. Parisian 

 Eocene. This section is based on the figures and diagnosis cited. 



Subgenus Lucinella Monterosato, 1883. 



Shell like Divaricella, but the ligament obsolete, and the resilium wholly 

 internal, as in Semele. Type Tellina divaricata Linne, better known as Lucina 

 commutata Philippi. Mediterranean. This is also the type of Cyclas Stoliczka, 

 1870, non Lamarck, 1799. 



Divaricella subrigaultiana O. Meyer. 



Lucina (Cyclas) subrigaultiana O. Meyer, Bull. Ala. Geol. Surv., i., p. 81, pi. iii., figs. 13, 

 133, 1886. 



Vicksburgian Oligocene at Vicksburg, Mississippi ; Meyer. 

 This is the earliest species of our Tertiary so far reported. I have not seen 

 specimens. 



