OBSERVATIONS ON TYPHLOMOLGE RATHBUNI. 95 



fore the present southern and northern parts of the Edwards 

 limestone were separated from each other, and that after the 

 dislocation in Eocene time part of the species was caught in the 

 caves of the Edwards limestone of the San Marcos area south 

 of the Balcones where it lived completely isolated from the rest of 

 the species. Since the specimens obtained from Ezell's Cave and 

 the Artesian Well are identical, it would mean either that the 

 species remained absolutely unchanged since Eocene time, or if 

 it changed, underwent exactly similar changes in the open ponds 

 of the subterranean Purgatory Creek and in the completely closed 

 and water-filled subterranean caves of the Artesian Well. It is 

 evident that none of these possibilities is probable. 



Not only the Artesian Well at San Marcos but numerous other 

 artesaan wells along the Balcones escarpments are supplied from 

 the sweet water horizon ; yet from none of them, except the San 

 Marcos Well, Typhlomolge has ever been reported. This would 

 be explained if the San Marcos Well contains besides the sweet 

 water also the Purgatory Creek water, since this certainly could 

 not be true for the other wells. Probably the Purgatory Creek is 

 the original habitat of the Typhlomolge and later on the animals 

 migrated down to the water channels of the Artesian Well. 



Also in none of the fissure springs of the Balcones scarp line, 

 not even in the San Marcos springs though they all come from 

 the sweet water reservoirs, Typhlomolge ever has been collected. 

 The same explanation as to the artesian wells could be applied 

 to these springs, if a communication exists between the Purga- 

 tory Creek System and San Marcos well. 



Finally an incident may be mentioned here which also would 

 speak in favor of the existence of a direct communication between 

 the Artesian Well and the Purgatory Creek System. Mr. Mark 

 Riley, superintendent of the U. S. Fish Hatchery, informed me 

 that in the basin of the Artesian Well a number of catfish were 

 kept at one time, but they disappeared gradually from the basin 

 and it is claimed that they migrated into the tube of the artesian 

 well. The writer is not prepared to form an opinion concerning 

 the probability of such migration. One day, however, while I 

 was looking for Typhlomolge in Ezell's Cave, I saw some fishes 



