OF CONCtlOLOGY. 3(>9 



in St. Thomas and St. John. Macroceramus {M.microdon, Pfr.) 

 inhabits Porto Rico, St. Thomas, St. John and Tortola, and M. 

 signatw, Guild., Tortola and Anguilla, the latter on the St. 

 Martin bank. Slrophia occurs in Porto Rico, St. Croix (sub- 

 fossil), Anegada and subfossil remains only of a species on 

 Sombrero. Megalomastoma, Alcadia, Macroceramus, excluding 

 Pineria, treated as subgenus of it by H. and A. Adams, 

 and Strophia, S. uva, L., of Curacao alone excepted, are not 

 represented in the Guadeloupe subprovince.* 



Helix nutabilis, Shuttl., is found in St. T hernias (subfossil), 

 St. John, Tortola and Anegada of the Virgin bank, and in St. 

 Bartholomew of the St. Martin bank, but not in the Guade- 

 loupe subprovince. 



Dentellaria (subgenus of Helix), of which H. mix denticu- 

 lata, Chem., and H.formosa, Fer., are types, is especially char- 

 acteristic of the Guadeloupe subprovince. It is represented 

 in Barbuda and Antigua by H.formosa, in St. Kitts by H. Jo- 

 sephinse, Fer., subfossilf), and occurs also in Guadeloupe, Do- 

 minica, Martinique, Barbados. &c., but not in the Porto Rico 

 subprovince. H. castrensis, Pfr., of Porto Rico, placed by Al- 

 bers in Dentellaria, and by Pfeiffer with species of that type, 

 is a questionable exception, — it appears to me to belong to the 

 same group as H. notabilis, and H lima, Fer., — of the latter, 

 indeed, I have considered it a variety. 



The species common to the Porto Rico and Guadeloupe sub- 

 provinces, of which a list is annexed, are few, and of a char- 

 acter, their general distribution also considered, favorable to 

 my views as to the separation of the two faunas. 



(Those marked * occur also in one or more of the other sub- 

 provinces, ** also in North America, f also in South America.) 



* I have already noticed that Megalomastoma and Strophia do not occur 

 in Jamaica, the most southerly of the larger islands, and that Macroceramus 

 is there represented by M. Gossei, Pfr , only, — a species found also in Cuba 

 and Florida. 



t The occurrence in St. Croix, St. Thomas, Sombrero and St. Kitts, of 

 subfossil, or at least of species not now living on those islands, is a subject 

 of much geological interest. 



