ART. 20 PLORroA TREE SNAILS SIMPSON 37 



Sable; Chokoloskee; Long Pine Key; Cox's hammock; Snapper 

 Creek; Costello's hammock; Miami hammock; Pinecrest, south-cen- 

 tral Everglades, not typical. 



A striking and very variable form, probably a hybrid, which com- 

 monly bears the name of the " black snail " ; and, considering its 

 rarity, it has a wide distribution. Rarelj'^ a shell shows bluish or 

 greenish cloudings like "versicolor^ and one specimen from Key Vaca 

 is marked very much like the lighter-colored forms of that sub- 

 species. In one shell from the Miami hammock and another from 

 Snapper Creek the axial whitish strigations continue to the base, and 

 there is a dark peripheral band without a light center. One shell 

 from Vaca is very thin and inflated and bears some resemblance to 

 Oxystyla resiis. Without a doubt this form has been an inhabitant 

 of the Chokoloskee region. A Mr. House, who resided there, took me 

 in his boat to a place where there was formerly a fine hammock 

 where he said he found the black snail, but it had been cut down and 

 made into a field. We found dead shells there which still showed 

 that they were tnarmorojtus. It is a nondescript and combines 

 characters of fasciatus and crenatius. 



I have no doubt but that this or an analogous form inhabits or 

 has recently inhabited some part of Cuba, although, so far as I 

 know, nothing like it has been found, and that it has migrated and 

 become established on Key Vaca, from which it spread along the 

 Upper Keys and crossed to the mainland on the old land bridge. 

 It reached Chokoloskee on the southwest coast and has probably 

 been swept across to the rocky ridge during time of a tidal wave. 

 On this ridge it has again hybridized, this time with forms of 

 fdsciatus^ and has produced versicolor on Long Pine Key; cas- 

 taneits, which has spread up to the Miami hammock; and at the 

 latter place it has developed into testudineus. Throughout this 

 ridge occasional shells are found which have the entire axial region 

 pure white, and these I refer to inarmoratitis. 



LIGUUS CRENATUS VACAENSIS Simpson 



Plate 4, fig. 10 



1920. Liguus crenatus vacuensis Simpson, Proc. Biol. Soc. Washington, vol. 3S, 

 p. 122. 



Shell usually large, with convex spire, subsolid to solid, with deep 

 sutures and the last and penultimate whorls slightly flattened, white 

 or shaded greenish with sometimes a few spiral green or bronzy 

 lines on the body or base ; texture somewhat porcellanous ; columella 

 heavy and twisted or truncated. 



Length of type 54, diameter 27 mm.; length of large shell 64, 

 diameter 33 mm. 



