FREE INSTITUTE OF SCIENCE 



TERTIARY FAUNA OF FLORIDA 



its distribution. I have seen no specimens from south of North Carolina. 

 The subgenus Perissodon of Conrad was never defined, and rests upon purely 

 specific characters. His G. minor is merely a young shell of the same species. 



Section Afioniiigiti Dull. 

 Rangia Johnson! Dal I. 



PLATE 22, FIGURK 18. 



<;ii(t//it>i//i Jolniioni Dall, Trans. Wagner Inst., iii., p. 337, pi. 22, fig. 18, 1892 ; Proc. 

 U. S. Nat. Mus., xvii., p. 96, pi. vii., fig. 7, 1894. 



Chesapeake Miocene of the Pascagoula clays, at Shell Bluff, Pascagoula 

 River, Greene County, Mississippi ; also at a depth of seven hundred feet in 

 the artesian well at Biloxi, Mississippi, and seven hundred and thirty-five 

 feet in the artesian well at Mobile, Alabama; L. C. Johnson. 



This species is smaller and more peculiar in form than any of the others, 

 and presents the peculiarity (extremely rare in this family) of having the 

 superior cardinal tooth in the right instead of the left valve. The anterior 

 lateral tooth is shorter relatively than in any other species, and the shell is 

 more drawn out behind the beaks. 



In the Miocene (?) of Carrizo Creek,' Colorado Desert, California, Dr. 

 Leconte found a fossil species of Gnathodon, which was named G. Lecontei by 

 Conrad. It is nearest related to R. ciincata. A curious little shell is described 

 and figured by Harris in the Fifth Annual Report of the State Geological 

 Survey of Texas under the name of G. qnadriccntennialis. A careful examina- 

 tion of specimens submitted by Mr. Harris leads me to believe that the species 

 may best be referred to Sfisnla, as the cartilage-pit is not closed above. It is 

 found at a depth of twenty-one hundred to twenty-two hundred and fifty feet 

 in the Galveston artesian well, and belongs to the Upper Miocene. Rangia? 

 minor (Conr.) Whitfield, from the Miocene marl of Shiloh, New Jersey, is 

 founded on a young Jlhilinin in the collection of the U. S. Nat. Museum, and 

 is probably not identical with Conrad's species. Gnathodon / tennidens Whit- 

 field, based on an internal cast from the Cretaceous " Plastic Clays" of New 

 Jersey, is probably referable to Isocardia or some analogous form, and has 

 nothing but the prominent and distant beaks to connect it with Rangia. 

 Several foreign species referred by authors to Rangia are with little doubt 

 more correctly placed in other genera. No undisputed species of Rangia has 

 been found earlier than the Middle Miocene, or in any region exterior to the 

 North American continent. 



