98 EDUARD UHLENHUTH. 



of the main hall. In these pools certain crustaceans are found in 

 large numbers, which according to Dr. Ortmann, are at least very 

 closely related to if not identical with the species Stygonectes 

 flagellatus? an amphipod know r n from the San Marcos Well. 

 Thus, this animal, which through its mode of living is well 

 adapted to the conditions prevailing at present in Boyett's Cave, 

 is the only remnant there of the Purgatory Creek System fauna. 



THE SAN MARCOS SPRINGS. 



According to Hill and Vaughan it is quite certain that the San 

 Marcos Springs, like all other fissure springs along the escarp- 

 ments of the Edwards Plateau, are of the same origin as the ar- 

 tesian wells of this area, and hence the water of the .San Marcos 

 Springs comes from the same reservoir which supplies the Arte- 

 sian Well at San Marcos Fish Hatchery. We might expect there- 

 fore that between these two localities ways of communication 

 exist along which the Typhlomolge may travel. 



We have not so far subjected the San Marcos Springs to a 

 thorough examination, but a brief mention may be made of cer- 

 tain facts valuable for future exploration. The water of the San 

 Marcos Springs comes from funnel-like depressions of the sur- 

 face (see diagram, Fig. n), and forms a little lake which is the 

 head of the San Marcos River. The openings through which the 

 water emerges lie deeper (at an altitude of only 532 feet) than 

 the surface of the water of Purgatory Creek. The surface of 

 the lake which is artificially dammed, is 559 feet above sea level. 

 The temperature of the water in a little spring on the bank of the 

 lake is 21.5 C,, like that of the water of the Purgatory Creek 

 system and the Artesian Well. 



Towards the south the valley at the head of the River continues 

 and forms the bed of the San Marcos River in which the water 

 is flowing, but this valley can be traced also north of the springs, 

 though here it is dry. 



Unconfirmed claims have been made that the "white sala- 

 mander " was seen at the head of the river, but that it had de- 

 veloped eyes and turned brownish. These statements are, no 



i For further information see Benedict and Weckel. 



