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TERTIARY FAUNA OF FLORIDA 



Genus Halonympha Dall and Smith, 1886. Type Neara claviculata Dall. 



Surface concentrically striate or smooth ; hinge with an acute cardinal in 

 the right valve, no other teeth in either valve; the posterior hinge-margin is 

 buttressed by a long, sharp, clavicular lamina in both valves ; the fossette 

 small and central. 



The clavicle in this group receives the posterior adductor on its upper sur- 

 face, thus serving as a myophore as well as a buttress. 



Genus Myonera Dall and Smith, 1886. Type Necera paucistriata Dall. 



Surface with radiating or concentric sculpture or both; hinge edentulous; 

 fossette vertical or posteriorly directed, adherent by either margin. 



The value of the above groups may eventually be raised somewhat in sev- 

 eral cases. Professor Verrill has suggested generic rank for Cardiomya, though 

 this seems doubtful to me. Further information in regard to the very peculiar 

 anatomy of these forms is necessary before any final systematic arrangement 

 can be reached. In a general way recent Cardiomya seems to affect warm and 

 relatively shallow waters, the smooth Cuspidaria being found in colder, deep, 

 or northern waters. 



A fossil species of Cuspidaria was figured by Wilton in 1830, and the name 

 Ryderia proposed for it, but the species was not described or specifically named, 

 and I have not been able to find any other data in regard to it beyond the refer- 

 ences in Bronn and Herrmannsen. The group is known from rocks as early 

 as the Upper Jurassic, and Cardiomya was already differentiated in the later 

 Cretaceous. 



Our earliest Tertiary Cuspidaria (s. s.) is C. cequivalvis Whitfield, from the 

 Shark River, New Jersey, Eocene. The next, of nearly the same age, is a 

 species named alternata by Meyer and Aldrich from the Eocene of Lisbon, 

 Alabama; there was, however, an earlier species of this name (Neara alter- 

 nata (Orb.) Gabb), and it will best take the name of C. attenuata, by which 

 it is designated in the explanation to Mr. Aldrich's plate. The Neara? nasu- 

 toides of Whitfield, 1885, is imperfectly known; judging from the figures, it 

 does not belong in this family. 



Nearly all the other fossil species of this genus in our Tertiary belong to 

 the subgenus or section Cardiomya. C. prima Aldrich, from the Wood's Bluff 

 horizon, has the look of a Myonera, but may be left where it is until the hinge 

 is described. C. dolabriformis Gabb appears in the Eocene of California, but 

 is imperfectly known. C. multiornata Meyer and Aldrich, from Wahtubbee 



