NON-MARINE MOLLUSCS OF SURINAM. 37 
comparing this shell for me with the rich material of U nio- 
nidae, of which he disposes. He wrote to me it being a 
new species, related to D. caipira Ihering and D. eurhyn- 
chus Küster, perhaps also to D. divaricatus Lea. 
I have named this species in honour of its discoverer, 
Mr. F. Voltz, who was collecting in Surinam during the years 
1853—1856, and died there a victim of his unfatigable | 
activity. 
* 89. CASTALIA SULCATA Krauss (figs. 17 a—c). 
Castalia suleata, Krauss, Zeifschr. f. Malakozool. V, 1848, p. 99. 
Marowijne. Krauss. 
Litani. Gonini-Expeditie. 
Krauss, 1848, p. 99. Marowijne. 
Kappler, 1887, p. 2. Cataracts of the Marowijne. 
This species is larger than C. ambigua Lam., and has 
the concentrical wrinkles well developed al over the sur- 
face. The specimens in our collection are lacking the 
radiating riblets. The much eroded Litani-specimens are 
larger than the specimen from the Marowijne, obtained 
from Mr. Krauss himself. 
Marowijne-specimen: Length 56'/,; height at the um- 
bones 44'/,, largest 48, thickness 34'/, m.M. 
Litani-specimen: Length 70; height at the umbones 50, 
largest 52, thickness 43 m.M. 
As there is not existing in literature, as far as I know, 
a figure of this species, I have figured the Marowijne- 
specimen. 
* 90. CASTALIA AMBIGUA Lam. 
Castalia ambigua, Lamarck, Hist. nat. 2. éd., 1835—45, VI, 
p. 522. 
Unio ambiguus Lam., Küster, Syst. Conch. Cab., Ed. nov, 
Band IX, Abt. 2, 1851, p, 165, T. 48, f. 1. 
Nickerie. Voltz. 
Upper Saramacca River. Saramacca-Expeditie. 
Both specimens have the radiating ribs reaching only 
to the middle of the valves. This species, already reported 
from British Guyana, was not yet recorded from Surinam. 
Notes from the Leyden Museum, Vol, XXXVI. 
