538 MOLLUSCA. 
Hab. Nicaraeva: ina river at Tierra Blanca and Rio Malacatoya (Tate 5). 
Panama: Isthmus of Darien (H. C. Caldwell, U.S.N.). 
Clessin 4 points out rightly that the ligamental sinulus of the dorsal margin assigns 
to this species a place among the rounded South-American Anodonte. 
20. Anodonta depexa, sp. n. (Tab. XLI. fige. 8, 3 ac.) 
Testa solida, rhomboideo-obovata, modice convexa, sulcis levibus radiantibus et striis concentricis crispatis 
sculpta, olivacea, verticibus paulum prominulis, antice breviter rotundata, margine dorsali posteriore 
rectilineo paulum ascendente, angulo obtuso terminato, margine ventrali leviter arcuato, extremitate 
postica subrostrata, supra declivi, infra rotundata; facie interna pallide cerulescente, zona marginali 
opaca, submarginali valde iridescente; sinulus ligamenti triangularis, antrorsum versus, margine 
anteriore fere perpendiculari. 
a. Long. 67; alt. vert. 414, ale 45, diam. 24 millim. Vertices in 3 long. 
b. 4, 64; ” 393, 3 40, 45 233 9 ” 3 2 
"Ce 49 46 ; ” 29, 5 31, ,, 16 ” ” 3 
Hab. W. Guatemala: Paso Antonio, in the lower part of the Rio Michatoya (Stoll). 
99 
Three specimens of nearly equal size, and a younger one (¢), are before me, all 
having shallow furrows radiating from the summits towards the ventral margin, which 
cut the concentric strie of growth and cause them to become more or less frilled ; in 
the fore and hinder parts of the shell these furrows are not to be seen, and in the 
hinder part, at a determined line, they disappear and the concentric lines become 
simple, more crowded, and somewhat membranaceous and projecting, the appearance 
here being more dull and dirty, contrasting with the sumewhat shining olivaceous 
colour of the middle and fore parts. ‘This peculiarity is visible in all four examples, 
but in a somewhat different degree; whether it is due to the structure of the 
periostracum, or caused by the fore and middle parts of the length being more worn 
than the hinder part, it is impossible to say. I know of no other Anodonta or 
Glabaris with similar structure *; the general form and solidity of the shell, as well as 
the well-marked dull (lustreless) marginal zone, prove that it belongs to the South- 
American group of Anodonta latemarginata, Lea. 
21. Anodonta tehuantepecensis. 
Anodonta tehuantepecensis, Crosse & Fisch. Journ. de Conch. xli. p. 92 (18938)*; Miss. Scie. 
Mex., Moll. il. p. 526, t. 70. figg. 1, la *. 
According to Strebel’s specimens, very near the preceding (.4. depewa), also solid, with broad lustreless 
marginal zone on the inside and a triangular sinulus of the ligament; but somewhat more oblong, and 
with only a few feeble and scattered vertical furrows on the outside. 
a. Long. 56; alt. vert. 35, ale 364, diam. 193 millim. Vertices in 4 long. 
b, » 995 ” 34, ,, 36, » 203 ” + 
” 3 #99 
Hab. 8.W. Muxico: Cacoprieto, near Tapana, east of Tehuantepec (Sumichrast }2); Cerro 
Negro, near Santa Efigenia, State of Tehuantepec (Suméchrast, in coll. Strebel). 
* Perhaps A. chalcoensis, “ periostracum lamellated in the hinder part” (v. anted, p, 530), bears some resemblance. 
