168 PROCEEDINGS OF THE ACADEMY OF [March 



Guadalupe river 6 to 4 miles to the north; San Marcos river at San 

 Marcos, Hays county, on the dam above the fish hatchery (Pilsbry 

 and Ferriss; Singley); a variety from Bexar county (A. G. Wetherby). 



This form differs from Melania pluristriata Say (M. rubida Lea) of 

 central Mexico, by its far smaller size and less ample aperture. The 

 type of pluristriata measured 1.25x.oo inches; of rubida 1.30x.57 

 inches; and the specimens -from Lake Chapala examined by Dr. von 

 Martens from 26 x 12 to 35 x 13 mm., while no Texan shell we have seen, 

 in many hundreds examined, reaches 1 inch long. Von Martens refers 

 the Mexican species to Pachycheilus. Dr. William H. Dall, to whom we 

 submitted specimens of G. comalensis for comparison with the type of 

 M. rubida Lea, writes that "though the general form is the same, the 

 rubida is very much larger and perfectly distinct." The examples 

 figured are from Comal creek. New Braunfels, near the mill. 



The ascertained distribution of G. comalensis comprises only the 

 short rivers of a single small system emptying into Espirito Santo Bay, 

 intercalated between the Colorado and Nueces basins, and comprising 

 the Guadalupe and San Antonio rivers and their tributaries. 



The Goniobases are known from these streams only at the edge of 

 the "Edwards Plateau." As they live on rocks, etc., in swift water, 

 it is not likely that they approach much nearer to the Gulf. In the 



Fig. 29. Fig. 30. Fig. 31. 



Colorado river, where Pilsbry collected in 1885, nothing was seen of the 

 species, nor has it been reported from the Nueces or its branches. We 

 saw no sign of Goniobasis in the tributaries of the Rio Grande, where 

 our collecting was extensive enough to have found it if it existed.^' 



The operculum (fig. 29) consists of about four whorls, the nucleus 

 being situated at about the lower third of its length. It is closely 



^^ In the collection of the Academy there are several specimens labelled ' ' Dal- 

 las county," received from Mr. J. A. Single^^ This is in the Trinity river 

 drainage, but Singley in his catalogue of 1893, issued long after these specimens 

 were placed in thejcollection, expressly states that he found the species nowhere 

 but in Comal and Hays counties. There was probably some error in labelling 

 the^specimens. 



