DRYM^EUS, MEXICO AND CENTRAL AMERICA. 33 



GROUP OF D. SERPERASTRUM. 



D. DOMBEYANUS (Ferussac). PI. 26, figs. 1, 2, 3, 4, 5. 



Shell rimate-umbilicate, ovate-acuminale, white, solid, longitudi- 

 nally rugose. Spire acuminate ; whorls 7, flattened. Columella 

 nearly straight, brown. Aperture oval-oblong, brown in the throat : 

 peristome brown, very broadly expanded and reflexed ; the columellar 

 margin dilated (Pfr.}. Alt. G2, diam. 34, length of aperture 38 mill. 



Central Mexico : On t/ie slope of the liill Ajusco, near the city of 

 Mexico (ffahn, var.) ; W. Mexico: Venta de Zopilote, State of Guer- 

 rero (H. H. Smith). 



Helix dombeyana, Ferussac, in Mus. Paris, PFR. Symb. Hist. 

 Helic. ii, p. 76 (1842) (without description) Bidimus dombeyanus, 

 PFR. Symb. Hist. Helic. ii, p. 114 (1842), iii, p. 83 (1846) (first 

 description of the shell) ; Monogr. Helic. Vivent. ii, p. 57, vi. p. 38. 

 REEVE, Conch. Icon, v, Bulimus, pi. 30, f. 186. Bulimus (Dry- 



mceus) dombeyanus, PFR. in Malak. Blatt. ii, p. 151 (1855) Buli- 



multts (Otostonms) dombeyamts, v. MART, in Albers' Die Helic. ed. 

 2, p. 211 ; Malak. Blatt. xii, p. 23 (1865) Btdimulus (Scutalus) 

 dombeyanus, FISCH. & CROSSE, Miss. Scient. Mex., Mollusca, i, p. 



515 Lymn&a ruaosa. VALENC., in Humboldt & Bonpland's Obs. 



Zool.,ii, p. 250, pi. 56, fig. 5 vyoung) (1833). 



Bulimus alcantarcz, BERNARDI. Journ. de Conch., iv. p. 35, pi. 3. 

 fig. 1 (1853). PFR., Monogr. Helic. Vivent. iv, p. 393 Bidimidus 

 dombeyanus, var. P, FISCH. & CROSSE, Miss. Scient. Mex., Mollusca, 



1, p. 516 Bidimulus dombeyanus STREBEL, Beitr. Mex. Land und 



Siissw. -Conch, v, p. 74, pi. 7, fig. 3a, b. 



The largest species of the genus. The variety alcantara Bernardi 

 (pi. 26, figs. 4, 5) is distinguished by its white peristome. Von 

 Martens writes as follows : Of three full-grown specimens before me, 

 two exhibit the prominent edge of a former lip on the back of the 

 last whoi-1, one-third or one-half of the circumference backwards frcm 

 the aperture. The color of the peristome varies in these specimens 

 from very pale brown to white, which proves that B. alcantarce can 

 scarcely be distinguished even as a variety ; Strebel came to the same 

 conclusion. The interior of the aperture is also, in the variety, 

 brownish. The young specimen from Venta de Zopilote (pi. 26, figs. 



2, 3), has a pale-brown band immediately below the angular periph- 

 ery, as in the figure given by Valenciennes. 



