8 PROCEEDINGS OF THE AMERI0AN ACADEMY. 



Head Dr. Stimpson remarks : " The abundance of specimens of the 

 Archaeoplax at Gay Head indicate a warm climate in that region at the 

 time they were living. At the present day all Carcinoplacida? are inhab- 

 itants of warm seas. The nearest allied genus, Heteroplax, lives on the 

 coast of China at the northern limit of the torrid zone." 



The occurrence of a species of Cancer in the same bed does not nec- 

 essarily tend to prove that the water of the sea on our miocene coast was 

 not somewhat warmer than at present, though not of subtropical temper- 

 ature. There are four species of Cancer on the Pacific coast of North 

 America, where G. viaglster ranges from Sitka to Monterey, G. gracilis 

 from Puget Sound to San Francisco Bay, (7. loroductus from Paget 

 Sound to San Francisco, while G. antennarius occurs at San Francisco, 

 Monterey, and Tomales Bay. I am indebted to Miss Mary J. Rathbun, 

 assistant in the Smithsonian Institution, for the information that there are 

 no tropical species of Cancer, and she has kindly sent me the following 

 list of species of this genus exclusive of those of North America and 

 Europe : — 



G. novae-zelandiae Lucas. New Zealand. 



G. bellianus Johnson. Madeira. 



G. plebeius Poeppig. Chile. 



G. polyodon " " 



G. edwardsii Bell. " 



G. longipes Bell. " 



G. japonicus Ortmann. Japan 



G. pygmaeus " " 



G. gihhosuhis (de Haan) " as well as west coast N. America. 



G. amphioetus Rathbun " " " " " " 



Of the two species now living on the shores of southern New England, 

 the most common one ( G. irroratus) ranges from southern Labrador to 

 South Carolina, while G. borealis is rarer, more local, and has thus far 

 only been found to extend from Nova Scotia to Vineyard Sound and No 

 Man's Land. Both, then, appear to be on the whole boreal species. 



The invertebrate fauna with which Gancer proavitus is associated 

 has been enumerated by Dr. W. H. Dall.* Of twenty-two species of 

 mollusks, about eight appear to be recent species still living in the waters 

 of that region ; among them occur such boreal forms as Mija arenaria, 

 M. tnmcata, Toldia limatula^ sapotella, etc., and Dall states : 



* Notes on the Miocene and Pliocene of Gay Head, Martha's Vineyard, etc. 

 Amer. Jour. Sci. XLVIII., October, 1894, p. 296. 



