TRANSACTIONS OF WAGNER 

 1266 



TERTIARY FAUNA OF FLORIDA 



The animal of this species and of Mactra and some other bivalves w^as 

 called Callista by Poli, but the name was not used in binomial nomenclature 

 until 1852. The group is Dione Gray, 1847, not Gray, 185 1, nor Hiibner, 

 1816; and Venus Megerle, 181 1, not of Lamarck, 1799. Fischer cites Hystero- 

 concha in synonymy from Lang, who was nonbinomial. 



Section Lamelliconcha Dall, 1902. 



Shell trigonal, subcompressed, concentrically ribbed or laminate, without 

 spines, the escutcheon not defined, the edges of the nymphs smooth, otherwise 

 like Hysteroconcha. Type Cytherea concinna Sowerby. 



Seas of the tropics, especially west America. 



Cytherea perbrevis Conrad, 1848, from the Vicksburgian, is a Pitaria and 

 is as a rule more elongate and ovate-trigonal than would be supposed from 

 Conrad's figure, which represents an unusually short specimen. Meretrix 

 sapotensis Gabb, 1881, from the Oligocene of Costa Rica, and Caryatis 

 Guppyana Gabb, from the Pliocene clays of Costa Rica, near Moen, also belong 

 to this group. Circe (Lioconcha) Newcombiana Gabb, from the Pleistocene 

 of San Diego, California, and living on the same coast, may also be referred to 

 Pitaria. 



Pitaria ( Hsrpliantosoma ) carbasea Guppy. 

 Cytherea {Circe) carbasea Guppy, Quart. Journ. Geol. Soc. Lond., xxii., p. 292, pi. xviii., 



fig. 13, 1866. 

 Callista carbasea Gabb, Geol. Rep. St. Domingo, p. 250, 1873. 



Oligocene marl of Bowden, Jamaica ; Vendryes, Henderson, and Simpson. 



The peculiarity of this species, apart from its thin shell, recalling Callo- 

 cardia, is the fine, sharp, divaricate sculpture. In the Chipola species, about to 

 be described, the sculpture is still obvious, but its sharpness and clear definition 

 are gone ; in the Pliocene species the divarication may be observed by close 

 scrutiny on certain portions of the disk, but is absent elsewhere, and in some 

 fresh specimens can hardly be distinguished, and, finally, in the recent Pitaria 

 Simpsoni Dall, of the Antilles, no trace of such structure remains on the sur- 

 face. But let the shell be weathered and acted on by erosion and the intrinsi- 

 cally divaricate nature of the shell structure stands revealed. There seems to 

 be a difiference in endurance between the sulci and the ridges in such a shell, 

 with the consequence that under the action of water and carbonic acid the little 

 punctures due to erosion arrange themselves in divaricate lines, revealing 

 structure otherwise invisible. 



