On the Flora and Fauna of Santa Cruz. 119 



" The banks and islands forming the long Bahama chain di- 

 minish in size to the southeast, where are situated at its termi- 

 nation the submerged Mouchoir Carre, Silver and Navidad 

 Banks. In a similar manner, the submerged Virgin Island 

 Bank (with Anegadaon its northeastern extremity, geologically, 

 in the opinion of Dr. Cleve, resembling the Bahamas), Sombrero 

 and the Anguilla Bank, terminate the chain of the West Indies 

 (parallel with the Bahamas) eastward from Cuba." 



In a previous paper (Proc. Amer. Phil. Soc, 1871, 57) I en- 

 deavored to show, that the land-shell fauna of Porto Rico, with 

 Vieque, the Virgin Islands, Sombrero, Anguilla, St. Martin, St. 

 Bartholomew and Santa Cruz, is unquestionably the same. 



My present object is to show that Santa Cruz is connected 

 with St. Thomas, the fauna of both derived from Porto Rico, 

 in common with that of Sombrero and the islands on the An- 

 guilla bank, but by no means with Saba. 



Before discussing the statement of Prof. Agassiz as to the 

 connection of Santa Cruz with the northern islands of the Carib- 

 bean grouj) rather than with St. Thomas (of the Virgin group), 

 I would first shortly describe the general features of the geology 

 of Santa Cruz, and the character of its flora. 



Dr. P. T. Cleve (Proc. Royal Swedish Acad, of Sciences, 

 Stockholm, 1871) remarks : — "The geological formations of the 

 Island belong to different ages. The northern mountain ridge 

 is the oldest, and to judge from its great petrographical resem- 

 blance with the rocks of the Virgin Islands, it would seem to 

 belong to the same geological age as the latter, or the cre- 

 taceous. Upon those highly disturbed strata, very little dis- ■ 

 turbed beds of coralline limestone and white marls rest ; they 

 are probably of the miocene age. The youngest formation con- 

 sists of detritus swept down from the mountains by rains and 

 mixed with the white marls, and in a recent formation of cal- 

 careous sand around the shores." * * * 



"The recent formations of the island are partly terrestrial, 

 partly marine. The former covers a great deal of the surface 

 of the island in the plains below the mountains. It consists of 

 detritus and clay, sometimes mixed with white marl. In this 

 detrital mass are found shells of terrestrial mollusca, some of 

 Avhich are of extinct species and some no more extant in St. 



