MOLLUSCA. 651 
Lampsiuis (pp. 480, 509). 
ae certain number of the species here enumerated under this subgenus are also 
ated in the genus Lampsilis (division Heterogene) by Simpson. U. discus, Lea, 
which I regard as the Mexican analogue of the type of Lampsilis (U. ovatus, Say), is 
peed by him in the genus Unio (Homogene), section Elliptio, Raf.; U. sapotalensis, 
Lea, in Nephronaias; and U. cognatus, Lea, in Plagiola, section Amygdalopsis, the 
type of which is U. donaciformis, Lea. : 
Unio discus, var. panucoensis (p. 510). 
Simpson (/oc. cit.) makes a section, Lapidosus, within the genus Unio for U. lapidosus, 
Villa, evidently under the impression that it is a circum-Mediterranean form. Having 
compared Villa’s type in the Berlin Museum with Mexican specimens, I feel sure that 
it belongs to the same species, and that the pretended locality ‘“‘ Euphrates River” is 
erroneous. 
Unio tampicoensis (p. 511). 
The habitat Rio Pecos, Texas, is confirmed by Stearns (Proc. U.S. Nat. Mus. xiv. 
p. 104). 
39 (a). Unio rovirosai. 
Unio (Lampsilis) rovirosai, Pilsbry, Nautilus, xiii. 12, p. 140°. 
‘‘ Differing from U. wmbrosus [a var. of U. tampicoensis| in the narrower anterior end and consequently 
triangularly oblong form, the hinge-line and basal margin converging strongly forward ; the lateral teeth 
also shorter. Length 111, height 71, diam. 43 millim. The female is. much more swollen posteriorly than 
in U. umbrosus.” 
Hab. S.E. Mexico: Laguna de Arasta, near San Juan Bautista (Lovirosa'). 
Not figured. To be compared with U. alvenigenus. 
Evuiptio (pp. 481, 514). 
The greater part of the species enumerated under this subgenus are also admitted 
by Simpson in the section Edliptio (Raf.), type crassidens, Lam., of the genus Unio; but 
U. ravistellus, U. vellicatus, U. medellinus, U. eruginosus, and U. rowelli are placed by 
him in Nephronaias. 
Unio pliciferus (p. 514). 
I am glad to state that Simpson agrees with me in uniting U. pliciferus, Lea, 
U. carbonarius, Lea, and U. plexus, Conr., under one species; but, as a result of his 
bibliographical researches, he prefers the name U. plexus for the whole, Conrad’s 
description having one month’s priority. 
82* 
