180 MEGASPIRA. 



Genus MEGASPIRA 'Lea' Jay, 1836. 



Megaspira Lea, JAY, Catalogue of Recent Shells, edit. 2, 

 p. [81], for M. ruschenbergiana. LEA, Trans. Amer. Philos. 

 Soc., vi, p. 21 (June 15, 1838). Pyrgelix BECK, Index Moll., 

 p. 88, for P. elata = elatior Spix (1837). Balea sp., PFR., 

 Monographia, ii. Pupa sp. of various early authors. 



Shell rimate, cylindric-tapering, long and narrow, com- 

 posed of many (16 to over 20) narrow whorls, the last 

 rounded peripherally and beneath. Summit obtuse; proto- 

 conch of 21/2 to 3 finely striate whorls ; subsequent whorls ob- 

 liquely rib-striate. Aperture small, slightly oblique, but 

 slightly longer than wide. Peristome incomplete, the ter- 

 minations widely separated; outer lip narrowly expanded, 

 columellar lip triangularly dilated above. Parietal wall bear- 

 ing a median entering lamella, which penetrates several 

 whorls inward. Columella with two or three low emerging 

 lamellae, the median one of which (columellar lamella) pene- 

 trates nearly to the apex, and is enlarged and scalloped in 

 several of the later whorls; the other two lamellae (supra- 

 columellar and subcolumellar) penetrate less deeply, and are 

 relatively inconspicuous within. The later 3 or 4 whorls are 

 further obstructed within by a series of laminae radiating 

 from the axis upon the basal wall, at intervals of a third of a 

 whorl. There are no palatal plicae. Axis slender, perforate 

 or hollow. (Meg as, big, and speira, spire). 



Radula (of M. elatior robusta, pi. 31, figs. 1, 2) of the usual 

 oblong shape, composed of about 23.1.23 teeth of the ordinary 

 Helicid form, disposed in nearly straight transverse rows. 

 The central tooth is as wide as the laterals, with the square 

 basal-plate slightly longer than wide; tricuspid, the meso- 

 cone as long as the basal-plate, side cusps small. The lateral 

 teeth are similar, but asymmetrical by total suppression of 

 the entocone. The marginal teeth differ by shortening of the 

 basal-plates and the lengthening of the overhanging part of 

 both cusps ; the transition from laterals is gradual, the ninth 

 to twelfth teeth being transitional. Both cusps remain 

 simple and undivided to the edge of the radula. In the 



