350 



PORTO RICO 



in the south-west district of the latter island of Sagda (2 sp.). 

 The relative numbers of the genera StropMa^ Macroceramus, and 

 Helicina^ as given below (p. 351), are of interest in this con- 

 nexion. 



Porto Rieo^ with Vi^que, is practically a fragment of San 

 Domingo. The points of close relationship are the occurrence 

 of Oaracolus^ Cepolis^ and PartJiena among the Helicidae, and of 

 Simpulopsis^ Pseudohalea^ and Stoastoma, Oylindrella and Ma- 

 croceramus are but poorly represented, but Strophia still occurs. 



Fig. 231. — Examples of West 

 Indian Helices: A, Helix 

 (Parthena) angulata Fer., 

 Porto Rico; B, Helix (The- 

 lidormis) lima Fer., Vieque ; 

 C, Helix {Dentellaria) mix 

 denticulata Chem., Martin- 

 ique. 



The land operculates (see the Table) show equal signs of 

 removal from the headquarters of development. Megalomas- 

 toma, however, has some striking forms. The appearance of a 

 single Clausilia, whose nearest relations are in the northern 

 Andes, is very remarkable. Gaeotis, which is allied to Peltella 

 (Ecuador only), is peculiar. 



