TRANSACTIONS OF WAGNER 

 I I 80 



TERTIARY FAUNA OF FLORIDA 



that Sphcerella can be regarded at most as a section of Diplodonta, closely allied 

 to the typical forms of that genus. 



The genus may be divided as follows : 



Section Diplodonta s. s. Type D. lupinus Brocchi, Miocene of Italy. 



Shell rotund, equilateral, externally concentrically striated or smooth, with 

 inconspicuous epidermis ; two cardinal teeth in each valve, of which the right 

 posterior and left anterior are distally sulcate or bifid ; no lateral teeth ; the 

 hinge-plate when developed is usually excavated distally; there is no circum- 

 scribed lunule or escutcheon ; the adductor scars are subequal, continuous with 

 the pallial line, and close to the hinge-plate ; the margin is entire, the pallial 

 line simple, the pallial area often radiately striate ; anatomically the genus is 

 separated from Lucinidcs by its double gills and absence of siphon, and from 

 Cryptodontida by its generative and digestive glands being contained within 

 the general mass of the body. The excavation of the hinge-plate by which 

 Fischer would separate Felania from Diplodonta appears to be merely a specific 

 character, as is the turgidity of the shell, which varies widely among the 

 typical Diplodontas. 



Glocomene, Cydadicama, and Mittrea are synonyms. 



Section Felaniella Ball, 1899. Type Felania usta Gould, Japan. 



Shell like Diplodonta, but heavy, compressed, externally smooth, with a 

 conspicuous, usually dark epidermis, and less equilateral valves. 



To this group belong the shells referred to Felania by Carpenter and others 

 from the Pacific, D. apicalis Phil, from the Mediterranean, etc. 



Section Sphcerella Conrad. Type S. subvexa Conr. 



Shell large, concentrically striate, an impressed line above the anterior 

 cardinal suggesting a minute lunule ; the right posterior cardinal wide, undu- 

 lated above ; the posterior adductor scar distant from the hinge-plate. 



A single species known from the Miocene, and one (D. Verrilli Ball, = D. 

 turgida V. and S., 1881, not Conrad, 1848) from the Atlantic coast in deep 

 water. 



Section Phlyctiderma Ball, 1899. Type D. semiaspera Phil., Cuba * 

 (1836). 



* The shell from Japan, called by Dunker and others D. semiaspera, is a distinct 

 species, and will probably have to take the name of D. japonica Pilsbry. Philippi's type 

 was from Havana and may be the same as D. semireticulata Orb. (1845). All three 

 belong to the section. 



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