1907.] NATURAL SCIENCES OF PHILADELPHIA. 193 



May 7. 

 Arthur Erwin Brown, D.Sc, Vice-President, in the Chair. 



Twenty-one persons present. 



The Chair announced the death of William K. Shryock, a member, 

 April 28, 1907. 



The Publication Committee reported that papers under the following 

 titles had been presented for publication : 



"Description of New Species of Spioniform Annelids," by J. Percy 

 Moore (April 26). 



"A Contribution to the Morphology of Pyrula," by Burnett Smith 

 (April 29). 



"The Hymenopterous Family Evaniidse," by J. Chester Bradley 

 (April 3). 



Origin of the Tropical Forms of the Land Molluscan Fauna of Southern 

 Florida. — Dr. H. A. Pilsbry remarked that former writers on this 

 fauna have treated the tropical area in Florida as an outlier of the 

 Antillean zoological province. The speaker recognized two groups of 

 genera, of diverse origin: (1) Antillean genera, consisting chiefly of 

 species also West Indian, such as Chondropoma, Liguus, Cepolis, 

 Varicella, etc., concentrated southward, and unknown in the Floridian 

 PUocene, and (2) Mexican genera, chiefly composed of species confined 

 to Florida, such as Euglandina, Praticolella, Drymoeus of the dormani 

 type, and apparently Polygyra, some of which are represented in the 

 Floridian (Caloosahatchie) Pliocene. The first group he regarded as 

 recent additions to the fauna, which had reached Florida from Cuba 

 and the Bahamas by the agency of hurricanes, drifting trees and the 

 like. The second group probably emigrated from the Southwest during 

 the mild INIiocene climate, and entered peninsular Florida on the eleva- 

 tion marking the close of the Miocene. The Oligocene fauna of the 

 Tampa Silex beds, the speaker thought, had left no descendants. Its 

 snails were of wholly Antillean type, the lea ling Antillean genera of 

 Helices, Cepolis and Plcurodontc both being represented. 



Dr. Pilsbry alluded also to Prof. Alexander Agassiz's conclusion, that 

 the Florida Keys are in process of diminution by solution of the lime- 

 stone composing them. The former unity of keys now separated 

 accounts for the homoc'eneitv of their land-shell faunas. 



