PALEOGEOGRAPHIC SUMMARY 625 



Eoy S. Dickerson/ in the paper cited below, says regarding my conclu- 

 sion that the coral fauna of Carrizo Creek is of probably Pliocene age : 

 "His [Vaughan's] conclusions concerning the Pliocene age of these beds 

 rests upon the infirm basis of comparison with a JPliocene coral fauna of 

 Florida/^ and "All the coral genera except one occur in the Bowden or 

 associated horizons/^ The last statement is correct, and the first is cor- 

 rect in that I compared the fauna from Carrizo Creek with that from the 

 Pliocene Caloosahatchee marl of Florida; but Doctor Dickerson evidently 

 did not comprehend the entire basis for my opinion. The following 

 genera, now extinct in the Atlantic Ocean, but living in the Indo-Pacific, 

 occur in the Bowden marl and related zones, but are not known from 

 Carrizo Creek or from the Caloosahatchee marl : 



Placocyathus Antillia 



Placotrochus Syzygophyllia 



Stylophora Pavona " 



Pocillopora Goniopora 



Neither the coral fauna of Carrizo Creek nor that of the Caloosahatchee 

 marl, as at present known, contains any of the coral genera distinctive of 

 the Bowden and related zones. These distinctive genera became extinct 

 in the Atlantic during upper Miocene time, according to present infor- 

 mation. It therefore seems to me more probable that the fauna of Carrizo 

 Creek migrated to the head of the Gulf of California after these forms 

 had become extinct than that they were eliminated after migration at an 

 earlier period. 



Pliocene and later. — Subsequent to the Miocene there have been many 

 oscillations of the West Indian area, and during perhaps Pliocene time 

 there was profound deformation. Zeogeographic data, in the opinion of 

 several investigators, seem to demand former connection, probably during 

 late Miocene or Pliocene time, from Yucatan across Cuba to Haiti, Porto 

 Eico, and the Virgin Islands; from Honduras to Jamaica; and from 

 Anguilla to South America. It also appears that Saint Croix was once 

 joined to Anguilla and to the eastern end of the Virgin Islands. There 

 are certain geologically late fault-lines which perhaps date from this time, 

 and the severance of the old ridges into the islands we now know may be 

 largely due to movement along them. One of these fault-lines forms the 

 northern boundary of the Bartlett Deep and passes between the east end 

 of Cuba and the west end of Haiti. Another tectonic line which forms the 

 south side of the Bartlett Deep converges toward the former in the Wind- 



° Ancient Panama canals. California Acad. Sci. Proc, vol. 7, 1917, pp. 197-205 (date 

 printed with title, July 30, 1917; received by me on October 16, 1917). 

 ^° Added from Miss Maury's Santo Domingan collections. 



