1913] NATURAL SCIENCES OF PHILADELPHIA. 609 



from the volcanic part of the island, in St. Mary's, and is not now 

 living, so far as known, in the north of the island. I found it living 

 at Montpelier in the limestone district of the southeast extremity 

 of the island in St. Philip's Parish. I collected at St. George's 

 also the extinct Helicina named by Purves, Helicina crosbyi, which 

 appears to be a good species, not hitherto described or figured, but 

 his Succineas do not differ from the living Succinea harhadensis Guild. 

 These two Succineas found in this marl Purves has named S. boonii 

 and S. boonii var. elongata,^^ and he states that they are not now living 

 in Antigua, but they seem to me to be simply variations of the living 

 S. barbadensis Guild, which is found living everywhere in the limestone 

 district. It is to be noted that these so-called extinct forms are 

 larger than the normal living forms; and also a large "semi-fossil" 

 Succinea has been collected in Santa Cruz which belongs to the same 

 species as these from the horizontal marls. The Helicina crosbyi of 

 Purves is not known in the living state in Antigua, it seems to be 

 really extinct. It is not the species found in the neighboring island 

 of Barbuda, and more closely resembles one of the Jamaica species 

 of Helicina than any known species, but, as stated, it is probably a 

 good species. It is described with other undescribed species in this 

 paper. 



The list of species given by Purves of the land shells found in these 

 marls includes Cistula antiguensis Shutt., now living at Wetherill's 

 and near Montpelier, that is, at the northwest and at the southeast 

 corners of the island, but not seen living elsewhere; and also Subulina 

 octona Brug., found everywhere. The only really extinct form is the 

 Helicina crosbyi. None of the marine species observed are extinct, and 

 all are still living about the shores of the island. Such a deposit as 

 this one at St. George's (and similar ones are known along the north- 

 east and north shore to Boone's Point) was probably formed in much 

 the same way as the present salt ponds. It was at one time a 

 shallow bay, the mouth of which was cut off by the growth of man- 

 groves, and it thus became a lagoon. Into this lagoon, the washings 

 from the hills brought down the land shells that cover the ground, 

 even at present. This part of the island must have been grown up 

 in "bush" similar to the vegetation that now covers Barbuda, 

 in which bush Pleurodonte formosa, Helicina crosbyi, Cistida 

 antiguensis, Drymceus elongatus, Bulimulus guadalupensis, and other 

 land shells lived; and probably also the water of the lagoon, as it 



1® The authority placed after these species (Nob.) is a contraction for nobis and 

 means simply Purves. 



