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EDUARD UHLENHUTH. 



since so far it has been found to occur in all localities which are 

 inhabited by the blind salamanders. 



The cave of the San Marcos Well, thus, is characterized in the 

 following manner: (i) It is situated in the Edwards limestone. 

 (2) It contains water derived from the " sweet water " horizon. 



FIG. i. Basin of the Artesian Well of the U. S. Fish Hatchery in San Marcos. 



(3) The temperature of the water is approximately 21.5 C. (4) 

 The water is inhabited by the decapod, Palccmonctcs antrorum. 



FRANK JOHNSON'S WELL. 



Approximately two miles southwest of the San Marcos court 

 house (see map, Fig. 2), the flat valley of the dry Purgatory 

 Creek crosses the Balcones scarp line opening here into the flat 

 valley of the San Marcos River. Its northern slopes are formed 

 here by the San Marcos Hill. Purgatory Creek originates near 

 the Devil's Backbone, the divide between the Guadalupe and 

 Blanco Rivers, at Boyett's Farm, about 14 miles northwest of 

 San Marcos. It is dry at present, but several of the older in- 



