596 SUPPLEMENT. 
Potamomya ? 
C. B. Adams, Ann. Lyc. Nat. Hist. of N. York, v. pp. 549, 550 (1852), describes 
three new species of Potamomya, which he names equalis, inflata, and trigonella, found 
all three together 23 miles east of Panama, without giving any particulars concerning 
the sort of ground and the depth in which they live. Carpenter, Moll. West N. Am. 
p. 204 (1872), who has seen Adams’s specimens, believes that all three are probably 
individual variations of one species. The genus Potamomya (Azara, d’Orb.) is chiefly 
known from the southernmost part of America, from brackish water, but no other 
collector has found a species of it in the tropical part of the West Coast, so it is not 
unlikely that Adams’s shells are simply a marine form of Corbula. 
SUPPLEMENT. 
Tuis Supplement includes such additions to the fauna and corrections in the synonymy 
that have been noticed since the publication of the preceding pages, commenced in 
May 1890. Fischer and Crosse (Mission Scientifique au Mexique) have dealt with the 
Helicinide and a portion of the Cyclostomide subsequent to my enumeration of the 
species of these families (wnted, pp. 12-45), and I therefore quote their work in full. — 
Messrs. H. Pittier and P. Biolley have recently sent me various interesting forms 
from Costa Rica, some of which I have already dealt with in the preceding pages; the 
remainder will be noticed here. In giving the additional localities, the names of the 
main geographical regions previously mentioned in this work are included within 
square brackets. 
CYCLOTUS (p. 3). 
Cyclotus (Aperostoma) irregularis (p. 3). 
Cyclotus irregularis, Biolley, Mol. terr. y fluv. de Costa Rica, p. 3 (1897) °. 
To the localities given, add :— 
Hab. %. Costa Rica: San Miguel, Fl Reventazon, Santa Clara, and Carillo, 200-500 
metres above the sea (Biolley®); Valley of Tuis, 600 metres (Pittier: a banded 
specimen). 
S.W. Costa Rica: San Mateo, 250 metres (Biolley 5); Ravine of Vijaqual in the valley 
of the Rio Saveque; El Pital, in the valley of the Rio Naranjo; Alto de Mano 
_ Tigre, in the valley of the Rio Grande de Terraba; and Quebrada de Tocori, in 
the valley of the Rio Paqueta, 150-700 metres (Pittier). 
Biolley > states that the species does not occur on the elevated plateau of Central 
Costa Rica. 
