TERTIARY FAUNA OF FLORIDA, 



Superfamily SOLENACEA. 



Family SOLENID^. 



THIS group is quite ancient if we assume that tlie Paleozoic Paleosolen is a 

 member of it, which seems Hkely from the perfect correspondence of the 

 exterior form, though the hinge of Paleosolen is unknown. Want of suffi- 

 cient material obliges me to refrain from attempting any revision of the 

 groups older than the Tertiary, among which Soleiiaria Stoliczka (1870), 

 from the Turonian of Europe, and Legumen Conrad (1867), Legumenaia 

 Conrad (1858), and Solyma Conrad (1870), from the Cretaceous, may be 

 mentioned. 



The Solenida form a compact group after the elimination of the soleniform 

 Psamniohiida:, such as Novaculina and Tagclus. In the flattened species with 

 thin shells the valve is usually strengthened by a dorsoventral rib or clavicle; 

 in the strong cylindrical forms this is not needed and is not developed. The 

 foot is strong, extensile, and larger distally, where usually it can be expanded 

 laterally into a sort of disk by which the animal can pull itself rapidly into 

 its burrow as if by a mushroom anchor. Perhaps the security against enemies 

 which this arrangement gives is responsible for the great persistence of this 

 type in time. The siphons are short, more or less papillose or filamented 

 externally, and are more or less united, in those with long siphons only the 

 tips are separated. The beaks vary from subcentral to anterior ; the deep 

 burrowers have them most anterior for obvious dynamical reasons. 



The following arrangement is adopted : 



Genus Solen (L.) Scopoli, 1777. Type S. inarginatus Pulteney. 



Hinge with one cardinal in each valve; beaks nearly anterior; external 

 surface polished; valves usually straight. 



Section Solena Morch, 1853. Type 6". obliquiis Spengler. 

 Beaks stibanterior ; no anterior furrows ; periostracum rude, unpolished. 



949 



