Pleistocene Snails from San Patricio County, Texas 43 



Table 9. Measurements of Hawaiia minuscula in mm. 



Specimen 





Section 



and bed 



nos. 



Length 



Max. 

 diam. 



Min. 

 diam. 



Apert. 

 height 



Apert. 

 width 



No. of 

 whorls 



75, PI. 1, 



figs. 3a-c . 



.. 2,5 



1.1 



2.2 



2.0 



0.3 



0.5 



4 



Helicina orbiculata tropica "Jan" Pfeiffer 

 PL 1, figs. 2a-c. 



Description. Shell finely striate; apertural lip reflected onto the body whorl 

 with an apieally developed thickening; small but prominent "tooth" at the junction 

 of the columellar and basal margins. Shell, white with no color pattern preserved. 



Measurements. Measurements for Helicina orbiculata tropica are given in 

 Table 10. 



Distribution. Southern species: Arkansas; Texas, eastern part, to the Pecos 

 River in west Texas; Mexico, Coahuila, Tamaulipas, and Nuevo Leon (Pilsbry, 

 1948, p. 1084). 



Ecology. Helicina orbiculata tropica is a rather well defined subspecies. It is 

 able to withstand drouth; the species is found in the open areas as well as in the 

 more vegetated areas. 



Remarks. Helicina orbiculata tropica has been reported from the loess at 

 Helena, Arkansas (Shimek, 1917), from the Wisconsinan of Bee and San Patricio 

 counties, Texas (Sellards, 1940, p. 1637), and from the Berclair terrace of the 

 Medio Creek in Bee County (Conkin and Conkin, 1962, p. 348). 



Table 10. Measurements of Helicina orbiculata tropica in mm. 



Section 



and bed Max. Min. Apert. Apert. No. of 



Specimen nos. Length diam. diam. height width whorls 



31 2,5 



32, PL 1, figs. 2a-c .... 2, 5 



33 2,5 



34 2,5 



35 2,5 



36 2,5 



Helisoma tenue sinuosum (Bonnet) 

 PL 2, figs. 2a-c. 



Description. The present examples are apparently normal for the species. 



Measurements. Measurements for Helisoma tenue sinuosum are given in 

 Table 11. 



Distribution. Helisoma tenue sinuosum is apparently a south Texas species. 



Ecology. "Gastropods belonging to the genus Helisoma are inhabitants of 

 stagnant ponds, small lakes, and the quieter waters of streams" (Leonard, 1950, 

 p. 15). 



Remarks. Specific determination was made by Dr. J. P. E. Morrison. This is 

 apparently the first record of Helisoma tenue sinuosum from the fossil record. 



7.0 



8.5 



7.2 



3.1 



2.0 



4# 



6.9 



8.2 



7.0 



3.5 



1.9 



5 



6.9 



8.0 



6.9 



3.5 



2.1 



5 



6.5 



8.0 



6.7 



3.5 



2.0 



5 



6.5 



7.6 



6.2 



3.1 



2.0 



5 



6.5 



7.8 



6.5 



3.5 



2.0 



43/ 4 



