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1163 



TERTIARY FAUNA OF FLORIDA 



Kellia (sp.) Turton, Dithyra Brit., p. 57, 1822; Forbes and Hanley, Brit. Moll., ii., p. 94. 

 Bornia (sp.) Philippi, Moll. Sicil., p. 14, 1836; Deshayes, Moll. Algerie, I, Atlas, p. 103, 

 pi. 43, figs. 8-n (B. seminulum Phil.). 



The diphthong in the second syllable was used by Brown, a particular fol- 

 lower and friend of Leach, in the original publication, so there seems no reason 

 to doubt that it should be retained. 



Lasata is remarkable for having gills in which the inner lamina is both direct 

 and reflected, while the outer one is represented by the direct portion only. 

 The hepatic and generative glands are included within the general mass of the 

 body. 



The known species are nestlers, adhering by a byssus to the rugosities of 

 calcareous algae, barnacles, etc., and the young are long retained within the 

 parent shell. All the species vary from a purplish red to a pale-greenish yellow 

 and show a coarse epidermis under the microscope. The hinge shows a great 

 crudeness and, as it were, an amorphous constitution. Hardly any two indi- 

 viduals will show exactly the same development and form of the teeth. Nor- 

 mally there are in the left valve two laminae diverging from the subumbonal 

 region, where there is a minute pustular " cardinal." In the right valve a 

 similar " cardinal" and on each side of it a pair of laminae between which the 

 single lamina of the opposite valve is received. The so-called cardinal exists 

 in less than half the specimens examined, sometimes in one valve of a pair 

 and not in the other. The laminae are irregular, and part of them often missing. 

 The resilium is enormous in proportion to the size of the' shell, its ventral 

 surface with, in fully developed specimens, a thick, chalky layer which might 

 perhaps be regarded as a lithodesma. The resilium is inserted along the 

 ventral margin of the hinge-plate or laminary platform. 



The individual variation of these little shells is so great as to lend some 

 countenance to the old supposition that there is but one widely distributed 

 species in the genus. On the " new school" basis twenty-five or thirty species 

 must exist in British waters alone. I am inclined to believe that there are two 

 species, one Indo-pacific and Antarctic, the other common to the eastern North 

 Pacific, Florida, Bermuda, and European waters. There is great difficulty in 

 finding any constant differential characters, if they exist. Lascea rubra (Mtg.) 

 Brown is found in Southern California and Mexico, has very recently been 

 discovered in south Florida at Fort Worth by Dr. Pilsbry, has long been 

 known from Bermuda, and is a common European shell. The course indi- 

 cated by these localities is one which might coincide with the ocean currents 

 were the former passages across the American isthmus still open. 



