UNIO. 501 
22. Unio acutirostris. 
Unio acutirostris, Lea, Proc. Acad. Phil. 1866, p. 34°; Journ. Acad. Phil. (2) vi. p. 270, t. 35. 
fig. 84°; Obs. Gen. Unio, xii. p. 30, t. 35. fig. 84°, 
Unto sphenorhynchus, Crosse & Fisch. Journ. de Conch. xii. p. 296 (1893) *‘; Miss. Scient. Mex., 
Moll. ij. p. 617, t. 66. figg. 2, 2a’. 
Of ae size than U. liebmanni, rather even, not convex in the middle part of the length, very short and 
a most perpendicularly sloping before, prolonged and somewhat bent downwards behind ; ventral 
margin largely sinuated ; inside yellowish-white. 
Long. 78; alt. vert, 35, ale 30, diam. 25 millim. Vertices in + long. 
” 71; 9 35, ” 33, ” 27 9 ” 4 9 
Hab. Mexico (Sallé + 5), 
SouTH AMERICA, without nearer indication of locality (Patricio M. Paz 1~*), 
The above-quoted descriptions and figures seem to me to apply to one and the same 
species. It is to be regretted that no definite indication of locality is given in 
either case. 
23. Unio goascoranensis. (Tab. XX XVIII. figg. 10, 10a.) 
Unio goascoranensis, Lea, Proc. Acad. Phil. 1859, p. 118°; Journ. Acad. Phil. (2) iv. p. 258, t. 41. 
fig. 1897; Obs. Gen. Unio, vii. p. 76, t. 41. fig. 189°. 
Near U. acutirostris, but with the sides less flattened, the fore part a little more rounded, the ventral margin 
not sinuated, the hinder extremity less attenuated. 
a. Long. 584; alt. vert. 32, ale 27, diam. 20 millim. Vertices in 3 long. 
b. ” 65 ; : ” 33, ” 31, 9 23 ” ” % ” 
a. Lea’s figure; b. Specimen from Paso Antonio. 
Hab. W. Guatemata: Paso Antonio, Rio Michatoya (Stol/). 
W. Honpuras: River Goascoran, Pacific slope of Honduras (Leconte 1-8), 
The two Guatemalan specimens before me, one of which is here figured, are a little 
more lengthened than Lea’s type, but they agree so well in other respects that it is 
inadvisable to give them a new name. 
24. Unio tehuantepecensis. 
Unio tehuantepecensis, Crosse & Fisch. Journ. de Conch. xli, p. 296 (1893)*; Miss. Scient. Mex., 
Moll. ii. p. 618, t. 65. figg. 3, 3a, 4 *, 
Fore part similar to that of U. liebmanni; hinder half less attenuated; dorsal margin behind the summits 
at first nearly straight and horizontal, only from the hinder end of the lamellar teeth beginning to descend 
obliquely ; lower half of the hinder margin obliquely truncated ; ventral margin a little sinuated in its 
hinder half; inside whitish, with a yellowish or orange hue. 
Long. 68; alt. vert. 38, ale 36, diam. 24 millim. Vertices in 3 long. 
Hab. S.W. Mexico: near Santa Efigenia, Isthmus of Tehuantepec, State of Oaxaca, 
in a lake filling up the crater of a volcano (Sumichrast 1). 
Fischer and Crosse’s figures differ greatly in outline, fig. 4 being more equally 
attenuated behind ; but the latter may represent the younger state of this species. 
