UNIO. 519 
Near U. eruginosus, but differing from it in having the summits less advanced (in 
one-third of the length in U. radiatulus, in one-fourth in U. eruginosus), the cardinal 
teeth comparatively stronger, the ventral margin slightly arcuate in its whole length, 
and the hinder extremity somewhat more produced below. From U. yzabalensis it is 
distinct by the comparatively lower shell, the smaller cardinal teeth, and the absence 
of numerous and concentric ridges on the outside. 
The figure of U. calamitarum, Fisch. & Crosse (Miss. Scient. Mex., Moll. t. 64. fig. 5), 
resembles this species in outline, but differs from it in the form of the hinder end. 
&® 
52. Unio rowelli. 
Unio rowelli, Lea, Proc. Acad. Phil. 1859, p. 153°; Journ. Acad. Phil. (2) iv. p. 256, t. 40. fig. 136”; 
Obs. Gen. Unio, vii. p. 74, t. 40. fig. 186°, and xiii. p- 71 (animal) *; Tate, Am. Journ. of 
Conch. v. p. 160 (1870) °. 
Oval, a little produced before, attenuated behind, ventral margin much arcuated, with feeble triangular 
cardinal teeth. 
Long. 43; alt. vert. 25, ale 23, diam. 16 millim. Vertices in 3 long. 
Hab. Nicaragua: Rio Malacatoya and Rio Estar (Tate 5). 
N. Panama: Rio Chagres (Rowell 13), 
The summits are said to have undulate sculpture. 
53. Unio guatemalanus, sp.n. (Tab. XX XVIII. figg. 7-8 a.) 
Testa ovata, sat compressa, striis concentricis distinctis, intermixtis crassioribus sculpta, flavido-fusca, antice 
subproducta, supra et infra subequaliter arcuata, postice subrostrata, margine dorsali posteriore declivi, 
rostro obtuso, subtruncato, margine ventrali leviter arcuato, antice magis quam postice ascendente ; facies 
interna pallide livida ; dentes cardinales compressi, obliqui, crenati. 
a. Long. 574 ; alt. vert. 32, ale 30, diam. 174 millim. Vertices in 4 long. 
b. ” 563 ; ” 30, » 28, 4.19 ” 9 3 ” 
Hab. W. Guatemata: Paso Antonio, Rio Michatoya (Stol/). 
Two perfect specimens of this species are before me: one of them (8) agrees rather 
well in its general features with U. rowelit, Lea, except in the fore part of the shell; 
but the other (a) is remarkably higher, more compressed, more broadly rounded before 
and behind. Some single valves were also found at Paso Antonio, and these connect 
the two forms. 
There is no trace of peculiar sculpture on the summits. 
X. Unitomerus, Conrad. 
54, Unio manubius. 
Unio manubius, A. Gould, Proc. Bost. Soc. Nat. Hist. v. p. 229 (1855) *; Otia Conch. p. 218’; Lea, 
Obs. Gen. Unio, vi. p. 53°; Synops. Fam. Unionide, ed. 4, p. 54 (1870) *; Stearns, Proc. 
U.S. Nat. Mus. xiv. p- 105 (1891) °; Fisch. & Crosse, Miss. Scient. Mex., Moll. ii. p. 591°. 
Hab. N. Centrat Mexico: State of Chihuahua, sixty milesfrom Camp Ringgold (Webb). 
- Also found in Texas (Lea *). 
