78 Notes on Certain Terrestrial Mollushs. 



Although its contemporary and survivor, H. Bermudensis, is 

 nearly allied to it, I cannot refer to them as being identical. 



The occurrence of this large extinct form in Bermuda is 

 very interesting. It may surely be inferred that the species 

 lived at a period when the area of the land was more exten- 

 sive and elevated. The existiug form, it should be mentioned, 

 is also found sub-fossil. 



Wollaston (Variation of Species, 1856) remarks, with 

 respect to some large extinct Madeira Helices, that they may 

 have been but forms of the smaller living species, — "coex- 

 istent with them, though more sensitive to the great diminu- 

 tion of altitude and area which were consequent on the break- 

 ing-up of a once continuous land." 



Sub-fossil are not unfrequently larger than living allied or 

 identical forms. I have noticed that the sub-fossil Chond- 

 roj)oma? basicarinatum and cliordiferum of St. Croix are 

 larger than their very near ally C. Santacruzense, now living 

 on that Island. The extinct H. Josephine, found in St. 

 Kitts, is considerably larger than the living forms of the 

 neighboring Islands. St. Croix and St. Kitts, geologically 

 speaking, are but fragments of larger areas. 



Some living species, however, vary very much in size : I 

 may instance II. Luquillensis Shuttl. of Puerto Rico. The 

 measurements given by Shuttle worth are diam. maj., 40; 

 min. 32 mill. ; alt. 30 ad 33 mill. In the Swift cabinet 

 there is a remarkably small specimen, diam. maj., 29 ; min. 

 25 mill. ; alt. 18 mill. 



M. concolor, Fer., of the same Island is another instance. 

 In the Swift Cabinet there is one, 5£ whorls, diam. maj. 25 ; 

 min. 23 mill. ; alt. 9 mill. Adult specimens collected by 

 Dr. Cleve, having 4£ whorls, are not more than half that 

 size. Unfortunately, I have no note as to the stations of the 

 different sized forms. 



Guesteria Powisiana, Pfr. 

 M. Crosse (Jour, de Conch., 1872) described and figured 

 Helix Powisiana, Pfr., placing it in the new genus Guesteria, 



