502 
MR. H. N. RIDLEY ON THE 
upper portion of it being most prominent ; the tooth above it upon 
the body-whorl is single, bifurcating at the end. The three re- 
maining teeth are rather remote from the margin of the aperture. 
The anterior part of the last whorl just behind and parallel to 
the labrum exhibits a longitudinal swelling or varix, towards 
which the lip expands. 
5. Stenogyra (Opeas) octonoides, C. B. Adams. 
Sab. Jamaica, Cuba, St. Thomas. 
This species is more strongly striated than S. subula , has 
rounder whorls, a deeper suture, and a larger apex. 
Tour specimens were obtained at Platform Island. 
6. Stenogyea (Opeas) subula, Pfeiffer. 
Sab. Cuba, Porto Eico, &c. 
The specimens from Fernando Noronha agree exactly with 
examples of this species from Porto Eico. They were found 
beneath stones on the promontory between Chaloupe Bay and 
S. Antonio Bay. 
7. Stenogyea (Opeas) Beckiana, var. 
Sab. Island of Opara, Peru, Brazil. 
The shells from Pernando Noronha, obtained at the same spot 
as the preceding species, answer well to Pfeiffer’s description ; 
but they are more strongly costulate than Brazilian specimens 
with which I have compared them. 
III. FEESHWATEE SPECIES. 
1. Planorbis nokonhensis, sp. n. (Plate XXX. figs. 11-11 b.) 
Testa parva, valde compressa, superne in medio depressa, 
inferne subplauulata, albida, tenui, subpellucida ; anfractus 4, 
superne convexiusculi, striis incremeuti tenuissimis sculpti, 
inferne radiatim subplicati, ad suturam angustissime marginati, 
ultimus infra medium obtuse carinatus ; peristoma tenue, mar- 
gmibus callo filiformi junctis, superiore oblique arcuato. 
Diam. maj. 5 millim., min. 4g, alt. 1. 
This species is about the same size and shape as P. Gilberti, 
Dumber, and P . fragilis, Brazier, from Australia. The lower 
surface, however, is flatter, and the curve of the lip differeut 
