OBSERVATIONS ON TYPHLOMOLGE RATHBUNI. IOI 



A spring near Twin Sister Mountain, Hays County, 2 miles from 



Wimberly. 

 A spring near Ozona, 100 miles from San Marcos. 



SUMMARY. 



1. At present it is certain that Typhlomolge rathbuni inhabits 

 the subterranean water of the Purgatory Creek System just north 

 of the Balcones scarp line and one mile further up, and the caves 

 of the Artesian Well of the U. S. Fish Hatchery at San Marcos, 

 which seem to be in direct communication with the Purgatory 

 Creek System by means of channels about 200 feet deep. 



2. The populations of the species Typhlomolge rathbuni north 

 and south of the present Balcones scarp line have not been sepa- 

 rated from each other by the process of faulting in Eocene time, 

 but have developed in unrestricted communication with one 

 another. 



3. No certain data are available as regards the occurrence of 

 Typhlomolge in the San Marcos Springs and in the dry valley of 

 the San Marcos River north of the Springs. Since .the Springs 

 come from the same water reservoir as the Artesian Well, further 

 investigations should be conducted. 



4. All the localities containing Typhlomolge are located in the 

 Edwards limestone region, but the caves of the Artesian Well are 

 200 feet deeper than the rest. 



5. Typhlomolge have been found in the Purgatory Creek Sys- 

 tem at an elevation of approximately 585 feet above sea level. 

 Where this level could not be reached as in the upper Purgatory 

 Creek valley, only remnants of the Purgatory Creek System fauna 

 (Stygonectes flagellatum) were found. 



6. The water inhabited by Typhlomolge seems to be slowly 

 flowing water. 



7. The temperature of the water is approximately 21.5 C. 

 and it is inhabited by the decapod Palazmonetes antrorum. Since 

 the latter animal is much more numerous and can be detected 

 much easier than the Typhlomolge, its presence may be taken as 



an indication that the place is promising as regards the presence 

 of Typhlomolge. 



