364 MOLLUSCA. 
spirit-specimens of P. sowerbyana, d’Orb., I am compelled to separate the very closely 
allied P. spiculata, Morelet, from the subgenus Aplecta, in which it has been placed 
by Fischer and Crosse, and to include it in the new subgenus Stenophysa, the type 
of which is the Antillean P. sowerbyana. 
In the form of the shell the Mexican and Central-American species here referred to 
the subgenus Stenophysa are very like Aplecta, but may be distinguished by their paler 
colour, more narrow form, and the comparatively long and thin columellar margin of 
the aperture. 
7. Physa princeps. 
Physa princeps, J. S. Phillips, Proc. Acad. Phil. iii. p. 66, t. 1. fig. 11 (1846) °. 
Of the size and colours of P. (Aplecta) maugere, but much more narrowed downwards, the whole outline and 
that of the aperture being fusiform-elliptical; columellar margin very short, somewhat twisted and 
receding, forming a distinct angle with the basal margin. 
Long. 34, diam. 15; apert. long. 24, lat. 9 millim. Whorls 5-6. 
Hab. Yucatan (Norman '). 
This species is only known to me from the quoted description and figure; it cannot 
be identified with any of the forms figured in the works of Fischer and Crosse or 
Strebel, or present in the Berlin Museum. 
Var. pallens, n. (Tab. XIX. figg. 21, 22.) 
Agreeing in general form with the type, but unicolorous, pale yellow, very shining ; columellar margin rather 
thin, white, nearly straight. Aperture ? of the whole length. 
a. Long. 231, diam. 11; apert. long. 17, lat. 5 millim. 
b 864, 21, » 10; ” 15, , 5, 
Hab. Yucatan (Philippi, in coll. Dunker). 
The systematic position of this species is doubtful, as the form of its mantle-edges 
is not known, and the coloration resembles that of P. (Aplecta) maugere ; but judging 
from the more elongate and attenuate form of the lower part of the shell, and chiefly 
of the columellar margin, it seems to be best placed in the subgenus Stenophysa. 
8. Physa elata. 
Physa elata, A. Gould, Bost. Journ. Nat. Hist. vi. p. 379, t. 14. fig. 4 (1853)*; Clessin, in Martini 
& Chemnitz, Syst. Conch.-Cab. ed. 2, Limneiden, p. 268, t. 37. fig. 15°. 
Aplexa elata, P. Carpenter, Cat. Mazatlan Shells in Brit. Mus. p. 180°; Fisch. & Crosse, Miss. 
Scient. Mex., Mollusca, ii. p. 92, t. 82. fig. 2 (Aplecta) +. 
Bulinus elatus, Binney, Land and Freshw. Moll. N. Am. ii. p. 99, fig. 169°. 
Hab. LOowER CaLiFoRnia®. 
N.W. Mexico: Mazatlan, very common (fr. Reigen }-5). 
To the descriptions given by the above-mentioned authors, I may add that in the 
