138 PROCEEDINGS OF THE ACADEMY OF [March, 



The average size of 78 living shells is about 19 x 9 to 10 mm. Fig. 

 18 represents the largest shell taken, a dead one 26.5 mm. long. There 

 is but little variation in sculpture among shells from this place. 



Along the Rio San Filipe, not far from the Rio Grande, in chapparal 

 on the east side, we found numerous specimens differing from those 

 of Devil's river by having the rib-striae nearly obsolete on the last 

 whorl except just below the suture. A large number of dead shells 

 were found, but only very few living ones (pi. VI, figs. 23, 24). They 

 have the dull reddish, white-streaked coloration and the shape of the 

 Devil's river ragsdalei. 



Bulimulus dealbatus peoosensis n. subsp. PI. VI, figs. 26, 27. 



B. d. schiedeanus var., Pilsbry, Man. of Conch., XI, p. 132, pi. 17, fig. 6. 

 The shell is conspicuously calcareous, whitish with some fleshy or 

 sometimes corneous or ochraceous streaks ; upper whorls striate, the 

 last somewhat roughened by irregular growth- wrinkles. Spire long, 

 composed of numerous short convex whorls, the suture nearly hori- 

 zontal; apex white or pale; aperture small, usually ochre-tinted in 

 the throat, lip strengthened by a rib within. 



T)rpe locality, on the mesa about 1^ miles southeast of the eastern 

 end of the High Bridge of the Pecos (Southern Pacific Railroad), Val 

 Verde county, Texas. We found one small colony of this form, in the 

 midst of the large dark-mouthed B. alternatus marioe, and like that 

 chiefly living on Agave. The extent of the colony was perhaps not 

 more than 50 yards, but as the sun had already set, and we had just 

 emerged from the labyrinthine side canyons of the Pecos, we had 

 time to collect only about thirty-five specimens, each, most of them 

 dead. Everywhere else in the region around the High Bridge we 

 found only B. a. marice. 



This form is clearly a stunted race of the larger and less slender 

 B. schiedeanus of the Mexican fauna. B. schiedeanus has been con- 

 sidered specifically distinct from dealbatus by Binney and all the older 

 authorities, as well as by von Martens, who gives a series of good 

 figures in the Biologia Centrali Americana; but while the typical 

 schiedeanus is distinct enough, there are not lacking specimeiLs sug- 

 gesting intergradation with some forms of dealbatus. If schiedeanus 



