TRANSACTIONS OF WAGNER 



860 



TERTIARY FAUNA OF FLORIDA 



Sphenia attenuata n. s. 

 PLATE 35, FIGURE 9. 



Pliocene marl of the Caloosahatchie River, Florida ; Ball. 



Shell small, irregular, solid, wider, and rounded in front, attenuated be- 

 hind ; nearly equilateral, moderately inflated ; exterior with small, irregular, 

 concentric ridges and radial wrinkles due to irregularities of situs ; adductor 

 impressions large, especially the posterior ones; pallial sinus moderately 

 deep. Lon. 9.5, alt. 6, diam. about 4 mm. 



The most conspicuous feature of this irregular little shell is the attenua- 

 tion of the rather pointed posterior end. It is a decidedly heavier and larger 

 shell than 5. dubia. 



Genus TUGONIA Gray. 

 Tugonia Gray, Synops. Brit. Mus., p. 91, 1842 ; name only. Type Pliolas tugon Adan- 



son, = Mya anatina Ch. 

 Tugonia Recluz, Revue zoologique, p. 168, 1846. Type Mya anatina (Chemnitz) Gmelin. 



This genus has a reticulated sculpture and a globose shell, short behind, 

 with a posterior truncation forming a somewhat contracted hiatus, the beaks 

 quite posterior and the chondrophores subequal in the two valves ; pallial 

 sinus shallow ; shell of moderate size. 



(PSubgenus) TUGONIOPSIS Dall. 



Shell minute, externally with concentric sculpture or none, plump, 

 irregular, when normal very inequilateral ; beaks very posterior ; valves trun- 

 cate behind and gaping ; chondrophore of the left valve as in Mya, in the 

 right valve subumbonal, but becoming more prominent with age, as if seated 

 on a shelly callus; the hinge-margin grooved on each side of the beak, in the 

 right valve in the adult, with a dentiform projection behind the chondrophore 

 and unconnected with it, seated on the cardinal margin and recalling the 

 tooth in Corbula, but less prominent, and in the young hardly developed ; pos- 

 terior adductor scar very conspicuous and deeply impressed ; pallial sinus 

 moderate. Type : 



Tugoniopsis compacta n. s. 



PLATE 35, FIGURE 10. 



Miocerte of Magnolia, Duplin County, North Carolina ; Burns. 

 Shell small, plump, usually more or less irregular, and evidently a nest- 

 ler; surface finely concentrically wrinkled; beaks nearer the posterior end, 



