92 BULLETIN 68^ UNITED STATES NATIONAL MUSEUM. 



posterior angle acute; outer lip thin, showing the external sculpture 

 within; columella stout, somewhat reflected. 



The type (Cat. no. 16212, U.S.N.M.,) was collected by Xantus at 

 Cape St. Lucas, Lower California. It has 6 post-nuclear whorls, and 

 measures: Length 2.3 mm., diameter 0.8 mm. 



TURBONILLA (PYRGISCUS) TENUICULA Gould. 



Plate 8, figs. 3, 7, 7«,- 12, 12a, 14, 14a. 



Chemnitzia tenuicula Gould, Bost. Journ. Nat. Hist., vol. G, 1853, pp. 383-384, 

 pi. 14, fig; lb. = Chemnitzia terebrnlis Carpenter, Cat. Mazatlan Shells, 1856, 

 p. 432. = Chemnitzia unifasciata Carpenter, Cat. Mazatlan Shells, 1856, p. 433. 

 = Chemnitzia ? var. subcuspidata Carpenter, Rept. Brit. Assn. Adv. Sci., 

 1863, p. 659. = Chemnitzia crebrifilata Carpenter, Rept. Brit. Assn. Adv. 

 Sci., 1863, p. 659. = TurboniUa (Pyrgiscus) crebrifilata (Carpenter) Dall and 

 Bartsch, Mem. Cal. Acad. Sci., vol. 3, 1903, p. 276, pi. 2, figs. 6, 6a.= Tur- 

 honilla (Pyrgiscus) subcuspidata (Carpenter) Dall and Bartsch, Mem. Cal. 

 Acad. Sci., vol. 3, pp. 276-277, pi. 2, figs. 2, 2a. 



"Shell small, elongated, lanceolate, turrited, rather solid, shining, 

 wax yellow, a little dusky below the suture; whorls 10, flat, slightly 

 shouldered above, marked by about 20 direct, longitudinal folds, the 

 summits of which are cut by numerous fine revolving striae, deeper 

 in the interstices, which also extend over the base of the shell, though 

 the folds terminate at the periphery, or are extended in delicate fur- 

 rows; aperture narrow, ovate; lip sharp; revolving striee apparent 

 within. 



Dimensions. — Length 7.5 mm.; diameter 1.3 mm. 



Found at Santa Barbara." 



The above is the original description by Gould. Turhonilla (Pyr- 

 giscus) tenuicula Gould is the most abundant and most variable species 

 of all the west American forms, presenting man}^ varieties or incipient 

 species; to describe these would not aid science or the collector, but 

 would only add to the confusion which this paper is intended to dispel. 

 The following comprehensive description will embrace, we believe, 

 all the forms coming under this name : 



Shell slender to somewhat stubby and inflated, varying in color from milk-white 

 to waxy yellow or to dark brown, variously banded or plain monocolored; nuclear 

 whorls three, moderately large, planorboid, slightly slantingly immersed; post- 

 nuclear whorls rounded to flattened, contracted at base and strongly shouldered at 

 the summit, traversed by 18 to 28 strong vertical ribs, which are excurved and 

 usually somewhat thickened, and connected at their summits, which appear beaded; 

 these ribs extend feebly over the rounded base of the last whorl; the entire shell is 

 crossed by incised spiral lines, 10 to 16 or more of which appear on the exposed por- 

 tion of the whorls, and more, closer placed, wavy ones on the base of the last whorl; 

 the suture is deep, subchanneled and wavy; aperture ovate, produced at base; outer 

 lip thin, meeting the oblique, slightly curved and revolute columella in a broad 

 curve; a faint callus connects the posterior angle of the aperture with the insertion 

 of the columella. 



