GASTROCOPTA, NORTH AMERICA, WEST INDIES. 57 



c 3 . Teeth small, the basal fold usually wanting, 



upper palatal plica minute when present. 



d. Length 2.2 to 2.4, diam. 0.95 mm.; St. 



Thomas. G. riisei, no. 21a. 



d l . Slightly narrower, with deeper suture; 



Arizona. G. p. parvidens, no. 22d. 



d 2 . Length 1.36 to 1.55 mm., 4 to 4y 2 



whorls ; very thin and fragile ; Bimini 



Islands. G. p. dclicata, no. 22 &. 



16. GASTROCOPTA QUADRIDENS Pilsbry, n. n. PL 10, figs. 7, 10. 



"Shell narrowly perforate-rimate, conical-turriculate, with 

 the apex somewhat obtuse ; colorless, glassy ; surface very 

 slightly striated, shining; whorls 6, gradually increasing, 

 with the suture rather deep between the upper, less so be- 

 tween the lower whorls; the last whorl moderately ascending 

 at the aperture, rather rounded at the base, slightly expanded 

 near the aperture, with an impression over the inferior palatal 

 fold; aperture' rather oval, truncated above, margins well 

 everted, the palatal somewhat more curved than the columel- 

 lar, the two connected by a thin callous ; lamellae and folds 

 four, subequal; angrilo-parietal appearing almost simple, in- 

 clined toward the columella; columellar horizontal, rather 

 short and strong, palatals rather short and stout, in normal 

 position, the inferior somewhat larger and more remote from 

 the margin. Alt. 2.4 to 2.8, diam. 1.3; apert. alt. 1.0 mm." 

 (Sterki). 



New Mexico: Capitan Mts., Lincoln Co. (type loc. ; E. H. 

 Ashmun) ; Black Range, Sierra and Grant Cos. (Ferriss and 

 Pilsbry). Arizona: Bill Williams Mt., Coconino Co. (Pilsbry 

 and Ferriss) ; Mt. Mingus, near Jerome, Yavapai Co. (Ash- 

 mun) ; Santa Catalina and Chiricahua Mts. (Ferriss). 



Bifidaria quadridentata STERKI, Nautilus, xii, March, 1899, 

 p. 125. Not Pupa quadridentata Klein, 1853, also a Gastro- 

 copta. Bifidaria quadridcns Sterki, PILSBRY and VANATTA, 

 Proc. A. N. S. Phila., 1900, p. 607 (lapsus calami). 



This is a strikingly distinct species. By the very thin, 

 translucent, paraffine-white shell, without a crest behind the 



