FREE INSTITUTE OF SCIENCE 

 TERTIARY FAUNA OF FLORIDA 



low, with (in the adult) an almost linear depressed amphidet^^Ha, interrupted 

 by an oblique impressed subtriangular ligament pit wh^^Bmough external, 

 interrupts also the line of teeth ; interior smooth, musc^f impressions large, 

 not bounded by an elevated line; pallial line slightly indented below the 

 posterior adductor scar; there are about eight anterior and six posterior teeth, 

 small and delicate; basal margin smooth and nearly straight. Lon. 5.5, alt. 

 3.2, diam. 2.2 mm. 



This pretty little species recalls T. mi.rta Mayer and T. Baudoni of the 

 Paris basin, but is clearly distinct from either of the American species. 



Genus LIMOPSIS Sassi. 



The genus Limopsis is represented in the American Eocene, but, perhaps 

 owing to the fact that they were deposited in comparatively shallow water, 

 the Miocene and Pliocene of the United States have so far yielded no species 

 of this genus. Limopsis aviculoides Conr. (+ " Pectunciihis" obliqtuis Lea) 

 is found in the Gaibornian at Claiborne Bluff and Wahtubbee, Mississippi. 



The shell figured by Cossmann (Suppl. Greg. Mon., p. 16, pi. i, figs. 20- 

 21) as Limopsis pcrplana Conr. is distinct from any of the known species of 

 that genus in this formation, especially by its smooth inner margins, and may 

 take the name of L. Cossmanni. 



Limopsis radiatus Meyer is described by that author from Jackson, Mis- 

 sissippi. It is very close to and doubtless the descendant of the L. aviculoides, 

 but has a different sculpture. The latter, according to Gregorio, was referred 

 to L. nana Desh. by d'Orbigny, which is an erroneous identification, as pointed 

 out by Cossmann. Bronn did not make it, as erroneously indicated by Greg- 

 orio (Mon. Faun. Eoc. Ala., p. 193), nor did Conrad or Heilprin. The typo- 

 graphical errors in Gregorio's work are almost endless, and this appears to 

 be one of them. 



In the researches necessitated by the present work I have been obliged 

 to go over this group in the Claibornian, and find the errors so numerous 

 in every author who has treated of them, in spite of some rectifications by 

 Cossmann, that I feel the student will find the results useful, and so include 

 them here. The following groups of species have been referred erroneously 

 to Limopsis. 



Trigonoarca Conrad, 1867. Type Cucidlaa maconensis Conr. 



This genus, which begins with large species in the Upper Cretaceous, is 



