16 BULLETIN 90, UNITED STATES NATIONAL MUSEUM. 



Doctor Vaughan has gathered data at several other localities indi- 

 cating the presence of a fauna allied to or perhaps identical in some 

 cases with that found at Oak Grove ; a notable instance is the outcrop 

 at Shoal Eiver, Florida. 



As a group (which may later be enlarged) these faunas should be 

 separated from those included with the Orthaulax zone, in the writer's 

 opinion, for the reasons above given. It is entirely possible, and 

 more or less probable, that with such intensive study as has been 

 given to the Tertiary of the Paris basin in France, numerous other 

 faunas or subfaunas may eventually be given a place in the column 

 of the Florida Tertiary, but with such a vast field, so few workers, 

 and the topographic difficulties presented by most of the region, 

 progress must necessarily be slow. 



The following list presents in descending order the names of the 

 zones as now indicated with the designations used by the writer in 

 United States Geological Survey Bulletin 84, 1892, page 157. 



Zone of — Designations of 1892. 



Scapharca dodona Alum Bluff beds. 



Gardium cestum Chipola marl. 



Orhitolites fioridanus Tampa limestone. 



Orthaulax pugnax Orthaulax bed. 



RELATIONS OF THE FAUNA OF THE ORTHAULAX PUGNAX ZONE. 



The number of species and varieties of mollusks now known from 

 the zone is 312. Of these nearly two-thirds are peculiar to the zone 

 and have chiefly been obtained from the silicious layer. Of the total 

 moUuscan fauna 219 species were new to science when first explored 

 by the United States Geological Survey, and 95 of these are de- 

 scribed in this monograph. Of the previously known species 15 

 were named by Conrad and 29 by Heilprin, while 36 were first 

 described from other horizons by various writers. There are 9 

 species distinct from the others but represented by specimens too 

 imperfect to serve as the basis of descriptions. 



Of the species enumerated one seems undistinguishable from a form 

 of the same genus {Xenophora) which occurs in the upper Creta- 

 ceous (Ripley horizon) of the Gulf States and appears to survive 

 into the recent fauna of the West Indies. 



Four species go back as far as the Claiborne Sands, 6 are found 

 in the Jackson Eocene, and 7 in the Vicksburg. Eight come up from 

 the Lepidocyclina zone, 4 have been recognized in the scanty fauna 

 known from the Nummulitic zone, and one or two from the very 

 imperfectly explored Chattahoochee fauna. Eight are known from 

 the Tertiary of Santo Domingo, several of which are very charac- 

 teristic of the zone. The two characteristic species of Orthaulax 



