EXPLANATION OF PLATES. 673 
Fig. 5. Unio gabbianus, Lea (p. 498), Lake of Nicaragua: 5, seen from \ 
above, showing the unequivalve summits. | 
nuculinus, Phil. (p. 509), Nicaragua, specimen from Dunker’s 
collection, given probably by Philippi himself to the Berlin 
Museum : 6 4, seen from above. a, right valve, 
7. —— medellinus, Lea (p. 517), Rio Medellin, obtained by H. H. ( inside. 
Smith: 7 4, seen from above. 
radiatulus, n. (p. 518), Paso Antonio: 8 d, seen from above. | 
yzabalensis, Cr. & Fisch. (p. 507), Panzos, three different | 
forms selected from a large number of shells collected by Conradt. J 
6. 
8. 
9-11. 
PLATE XI. 
Figs. 1-7. Anodonta coarctata, Anton (p. 525), Lake of Chapala, different stages and forms 
obtained by Richardson at the same locality: 1, hinge and sinulus of right valve; 
2, summits of a young specimen, ?, showing the folds; 3, nearly full-grown ; 4 and 5, 
young; 6, normal, a, seen from above ; 7, rather abnormal example. 
exilior, Lea (p. 530), Vera Cruz, different forms selected from a large number 
of shells collected by F. D. Godman: 10a, hinge and sinulus of right valve; 10 4, seen 
from above. 
8-11. 
PLATE XLI. 
Figs. 1,2. Anodonta richardsoni, n. (p. 529), Ameca: 1, young; 14, summits of the same, 
enlarged, showing the undulated folds; 2, full-grown; 2 a, right valve, inside. 
3. (Pachyanodon) depexa, n. (p. 538), Paso Antonio: 34, right valve, inside; 30, seen 
from above. 
A., (Pseudoleila) ciconia, A. Gould (p. 536), Mazatlan, right valve, inside, showing the 
oblique scratches, mentioned on p. 537. 
5. Mycetopus subsinuatus, Sow. (p. 540), Paso Antonio: 5 a, right valve, inside. 
PLATE XLII. 
1-3. Polymesoda mexicana, Brod. (p. 548), Mazatlan: 1 and 3, younger specimens; 2, full- 
Figs. 
: grown; la, 26, and 3a, seen from above; 2a, right valve, inside, showing the 
pallial sinus. 
4, 5. placens, Hanl. (p. 545), Livingston: 4a and 5a, right valve, inside; 46 and 54, 
seen from above. 
6. olivacea, Carp. (p. 541), Mazatlan, young specimen: 6a, seen from above. 
7 cordata, Wiegm. (p. 546), Mexico, type-specimen in the Berlin Museum: 7 a, right 
valve, inside; 7 4, seen from above. 
8, 9. solida, Phil. (p. 544), Nicaragua, specimens from Dunker’s collection: 8a and 9a, 
right valve, inside; 8 4 and 94, seen from above. 
BIOL. CENTR.-AMER., Terr. and Fluviat. Mollusca, Apri] 1901. 85 
