374 MEXICAN BOUNDARY SHELLS— BALL. vol.x(x. 



Summary. — The collections made by the Commission in the Central 

 region cover thirty-nine s])ecies and varieties, of whiclx seven belong- 

 strictly to the Mexican fauna, as far as yet known. Twenty-four of 

 these are land shells, of which half are new, and one new Unio belong- 

 ing to the same general region brings the number of new species \\\\ 

 to twelve. Doubtless a thorough examination made during a rainy 

 period would add several species to this list, but considering the cir- 

 cumstances under which the collection was made, and the arid and 

 unfavorable character of the region, it would seem that Dr. Mearns 

 met with unexpected success. As a whole, omitting species of uni- 

 versal range, it would seem that the land shell fauna represents a 

 northward extension of the mountain fauna of Mexico, rather than a 

 moditication of the molluscan life of regions north, west, or east of the 

 territory- explored. So little is known of the Mexican mollusks that 

 extended comparisons can not at present be made. Only two of the 

 land shells are common to other regions than Mexico and the south 

 central basin Avest of the Atlantic drainage, a fact which emphasizes 

 the insular character of the mountain tops and the faunal distinctness 

 of their population. 



SPECIES OF THE TEXAN EEGION. 



The following species belonging to the Texan region of the Eastern 

 fauna were collected by Dr. Mearns: 



GLANDINA TEXASIANA, Pfeiffer. 



A few dead specimens at Fort Clark, Kinney County, Texas. 



BULIMULUS DEALBATUS, Say. 

 Numerous, mostly dead specimens. Fort Clark. 



BULIMULUS DEALBATUS RAGSDALEI, Pilsbry. 



This small and strongly striated variety of B. dealhatus was as com- 

 mon at Fort Clark as the normal form with which numerous interme- 

 diate specimens completely unite it, though extreme specimens seem 

 very distinct. 



POLYGYRA THYROIDES, Say. 



Immature specimens feeding on the leaves of Phaseolus. 



POLYGYRA TEXASIANA, Moricand. 



Found at Fort Clark and Fort Worth abundantly, the range of the 

 species, so far recorded, extending from Fort (iibson, Indian Territory, 

 south and west to the State of Tamaulipas, Mexico. 



POLYGYRA (MESODON) ROEMERI, Pfeiffer. 



A single specimen at Fort Worth. 



