TRANSACTIONS OF WAGNER 

 I 304 



y TERTIARY FAUNA OF FLORIDA 



Psilopus -f Psilopoderma Poli, Test. Utriusq. Sicilian, ii., p. 253, 1795 (nomenclature not 



Linnean). 



Psilopus Oken, Lehr. d. Naturg., p. 231, 1815. 

 Psilopododerma Agassiz, Nomencl. Index, 1848. 

 Lacinia " Humphrey," Mus. Calonn., pp. 53, 85, 1797. 

 Maceris Modeer, K. vetensk. Ac. nya Handl., xiv., pp. 174, 182, 1793. 

 Planospirites Lamarck, Syst. An. s. Vert., p. 400, 1801 (fide Deshayes MS.) ; Bosc, Hist. 



Nat. Coq., iii., p. 237, 1802; Roissy, Moll., v., p. 245, 1805; sole ex. P. ostracina Lam., 



from the Cretaceous of Maestricht. 



fHellia Schafhautl. (I have not been able to obtain this reference.) 

 Goossensia Cossmann, Journ. de Conchyl., xxxiii., p. 113, 1885; Cat. Illustr., ii., p. 102, 



1887. Type Cardita irregularis Desh. 



Omitting reference to the peculiar Mesozoic Chamidce for which no ade- 

 quate material is available, the typical members of the family appear only in 

 the later Cretaceous and reach their apogee in the Tertiary. The Tertiary and 

 recent Chamida include two genera, Chama and Echinochama, the latter 

 making its debut in the Oligocene. 



The Linnean genus was heterogeneous, and it remained for Bruguiere to 

 restrict the group to nearly its natural limits, excluding uncongenial forms. 

 Such names as Globus, Stola, Jataronus, Macerophylla, Psilopus, and Psilopo- 

 derma belong to pre-Linnean authors or non-Linnean nomenclature and have 

 merely an antiquarian interest. The group is tropical or warm-temperate in 

 distribution and world-wide in range. 



It has been very difficult to obtain material for determining the original 

 dentition in this group. Bernard had nothing less than five millimetres in 

 diameter, at which age those species with the largest protoconch have the hinge 

 much altered. Species with a small protoconch at that diameter show nothing 

 of the original hinge. The deep-water species and Echinochama have larger 

 protoconchs than the average species of the strand, and are therefore more 

 convenient for study, but in seventeen years search for protoconchs which 

 have not become attached has only resulted in obtaining two valves, though a 

 great deal of small material was picked over. By the study of the smallest 

 attainable fixed individuals something has been made out. (See pi. liii., 

 fig. i.) 



In all Chamas the protoconch is a small, polished, inflated shell, rounded or 

 subquadrate, which in average species reaches a diameter of 0.15 millimetres, 

 and, in such forms as C. congregata., C. pellucida, etc., almost immediately 

 shows in its growth the characteristics of the adult and becomes attached to 

 some convenient object when from three to five millimetres in diameter. The 



