1906.] NATURAL SCIENCES OF PHILADELPHIA. 141 
may be selected. The study of good series of shells taken at random 
and not selected shows that all lots of streaked shells are more or less 
mingled with white ones, and in colonies of toothed shells, fully adult 
and old individuals may be found without a tooth. On the other hand 
there seem, however, to be colonies without ragged-streaked individuals, 
and also communities in which no toothed shells are to be found. 
Perhaps the colonies containing mottle-streaked or toothed individ- 
uals are mixed or hybrid communities. It is a case where experiments 
on Mendelian lines by some one on the ground might be productive of 
valuable results. 
In illustration of the foregoing remarks, a few of the colonies repre- 
sented in the collection of the Academy may be noticed in more detail. 
In studying these races it is absolutely essential that the snails be col- 
lected alive. The colors, particularly of the interior, are evanescent 
and fade quickly on exposure to the sun and weather, though they 
change very little if at all in the museum. 
Corpus Christi, Nueces county (pl. VII, figs. 13, 14, 15, 16), collected 
by J. A. Singley. Of thick-set compact contour, strong, with a thick 
cream-tinted lip-rib, which is sometimes brown stained. Pinkish 
white, almost uniform with some very inconspicuous grayish or fleshy 
streaks. Not one ina lot of 43 1s marked with brown streaks outside. 
Interior varying from pale yellow to reddish brown, the darker tint 
exceptional. Columella varying from strongly toothed to nearly 
straight. Whorls 6, the earliest post-embryonic not distinctly striated. 
This form is the ‘‘binneyanus Pfr.’’ of Binney, intermedius Singley 
MSS. of Cockerell. 
Alt. 29 27.3 30 25 23 mm. 
Diam. 16 14.5 15 14 Pe 
Aperture 16.5 14 15.8 14 MESES 
At Hidalgo, Hidalgo county (pl. VII, figs. 17, 18, 19), the shells are 
more slender, white, rarely streaked throughout (fig. 17), but almost all 
of a series of 41 are variegated on the earlier whorls (fig. 18). Some 
are strongly toothed, but most shells have no columellar tooth. 
Interior brown. 
Alt. 30 29.5 29 28.5 mm. 
Diam. 13.5 - 13.5 13 1: eae 
Aperture 14 14.5 13.5 Lea * 
A series from Brownsville consists of similar but less elongated 
shells. 
