ABT. 20 FLOEIDA TREE SNAILS — SIMPSON 15 



enough to change the dry-land hammock into mangrove swamp, and 

 it needed only a slight depression to do this. Five of the forms — 

 castaneozonatus^ roseatus^ luteus, marmoratus^ and vacaensis — were 

 drowned out on Lower Matecumbe, but subcrenatus and lineolatus 

 survived, probably on a bit of hammock at the upper end of the island, 

 as this is a little higher than the rest of it. The snails were drowned 

 on the southwest end of Upper Matecumbe, which is slightly lower 

 than its northeastern part and is now nearly all swamp with only here 

 and there dry land. Long Key was carried down just enough to 

 drown out its Liguus. It is probable that a very slight upward oscil- 

 lation of this region since has made the latter island dry enough 

 for high hammock growth as a foot of elevation would change 

 swamp to dry land. But no Ligiius have landed on it since. 



During this last slight elevation of the mid chain a gravid speci- 

 men of the variety graphictis was landed (on drift from one of the 

 Lower Keys), probably on Lower Matecumbe, where it quickly 

 became established and soon began, to vary. Two of its forms, 

 lignunvvitae and shnpsoni are now living on the near-by Lignumvitae 

 Key, a mere dot of land just inside the regular line of the chain and 

 separated from Lower Matecumbe by a mud flat a little more than 

 a half mile wide. Another form which I have called delicatus is 

 found on Lower Matecumbe and on a small bit of hammock in the 

 swamp of the lower end of the upper island; also it was found 

 by Wurdemann long ago on Indian Key, another mere point about 

 half a mile outside the line of the regular chain and just olf the 

 lower key. I am inclined to believe that these outlying Liguus 

 reached Lignumvitae, Upper Matecumbe, and Indian Keys by drift- 

 ing during storms. 



In a part of Lower Matecumbe, where cross currents have eroded 

 and lowered the surface until it is no longer dry land, there is a 

 small hammock in which I found a fourth form of soUdus. The 

 shells are large, thin, of a glassy rather than porcellanous texture, 

 the ground color being a pale yellowish gray. They have the longi- 

 tudinal smears and a brownish peripheral band, and along this and 

 the sutures is a double row of squarish spots, while the entire axial 

 region is white. Because of its resemblance to pictus I have called 

 it pseudopictu^. Apparently it has rather recently developed in 

 this isolated hammock, and I found a few partly intermediate shells. 

 I have no doubt that it is the latest form of the genus to develop in 

 Florida. 



The species solidus seems to vary very easily and apparently has 

 broken into many forms. I found several interesting variations or 

 perhaps hybrids of what may be this species and some other near 

 Cabanas, Cuba, and I feel sure that before our hammocks were de- 

 stroyed in Florida there were several variations. I found shells on 



