TRANSACTIONS OF WAGNER 

 1228 



TERTIARY FAUNA OF FLORIDA 



Section Dosinia s. s. Type Le Dosin, Adanson,^ Dositiia africana Hanley. 

 Senegal. 



Lunule small, impressed ; escutcheon narrow elongate, flattish, bordered on 

 each side by a ridge or keel at which the concentric sculpture tends to become 

 lamellose ; lateral tooth small, smooth ; pallial sinus angular, ascending, usu- 

 ally narrow and elongated ; valves moderately convex. 



The escutcheon may be merely a flattening of the posterior dorsal border, 

 often unequal in the two valves, or it may be a well-defined area bordered by 

 distinct keel, more or less lamellose where the concentric sculpture intersects 

 the carina. Between these types almost continuous gradation may be traced. 



Section Orbiculus Megerle, 181 1. Type Venus exoleta Linne. 



In this section there is no escutcheon, the pallial sinus is very long and 

 narrow and the anterior lateral is smooth and strong ; otherwise it agrees with 

 Dosinia s. s. Arthemis (Poli) Oken, Artemis Conrad, Arctoe Risso, Arctoa 

 Hermannsen, and Cerana Gistel are synonyms. Orbiculus a of Megerle 

 is a typical Dosinia, and the second species of Orbiculus j8 was a Codakia. The 

 posterior cardinals in the young are not corrugated. 



Section Austrodosinia Dall, 1902. Type Cytherea amis Philippi. New Zealand. 



Lunule deeply impressed ; escutcheon impressed and bordered by prominent 

 keels ; pallial sinus short and angular ; anterior cardinals and especially the 

 anterior lateral with the pit into which it is received sharply corrugated. This 

 group is also represented in Japan. 



Section Dosinella Dall, 1902. Type Cytherea angulosa Philippi. East Indies. 



Valves suborbicular, with a shallow, flattish lunule ; the escutcheon narrow, 

 flattish, hardly defined ; pallial sinus deep, ample, ascending, bluntly rounded 

 at the anterior end ; anterior lateral and posterior right cardinal teeth absent 

 or obsolete. 



There are a few small species, such as D. hepatica Philippi, which have the 

 bight of the pallial sinus rounded instead of angular, but in this large form the 

 discrepancy is so marked, that, in connection with the obsolescence of the teeth, 

 it seems that a sectional separation is warranted. 



Section Dosinorbis Dall, 1902. Type Arthemis bilunulata Gray. Japan. 



Lunule and escutcheon deeply impressed, the former small, set in a large 

 impressed area which, like the escutcheon, is bordered by a lamellated keel ; 

 valves compressed, beaks produced ; the sculpture of the middle of the disk 



