MOLLUSCA. 647 
one to the other, only 3 on the visible part of the penultimate whorl; 3 remaining whorls. Aperture 
narrowly ovate or lanceolate; outer margin thin, little arcuated, basal margin narrowly rounded, 
columellar margin nearly straight, a little thickened, of a violaceous hue, obliquely notched below. 
Long. 14, diam. 8; apert. long. 8, diam. 4? millim. (Costa Rican specimen). 
Hab. N.E. Costa Rica: confluence of the Rio Shei and of the Rio Tararia (Pittier, 
Sept. 1898). 
CotomBia®: Justos, in the Rio Dagua (Hoépke, in Mus. Berol.). 
EcuaDor: Quito (Osculati 2). 
The localities “ Peru (Lieut. Humphreys1)” and “Brazil”? are too vague to be of 
any value. 
NERITINA (p. 465). 
Neritina latissima, var. globosa. 
To the localities given, add :— 
Hab. Satvapor: La Libertad (Aurel Krause, 1882, in Mus. Berol.). 
[S.W. Costa Rica:] El Pozo, Rio Grande de Terraba, 700 metres (Pittier). 
Neritina lineolata (p. 471). 
Neritina lineolata, Ancey, Ann. de Malace. ii. p. 256 (1886) *’. 
To the localities given, add :— 
Hab. F. Honpuras: mouth of the Rio San Estevan (St. Stephen), in fresh water 
(Ancey **). 
Ancey 22 also mentions WV. microstoma, Lam., as living at the same locality; this is 
probably the var. reclivata, Say, of the present species (anted, p. 472), which is found 
in other places in company with typical WV. /ineolata, although Ancey still separates 
N. microstoma from N. reclivata. 
UNIO (p. 478). 
Almost simultaneously with the issue of the concluding portion of my contribution 
on the Unionide, a very valuable “Synopsis of the Najades or Pearly Freshwater 
Mussels,” by Ch. T. Simpson, has been published [ Proc. U.S. Nat. Mus. xxli. pp. 501- 
1044 (Smithson. Institut. no. 1205)]. In this work the species are arranged 
according to the sexual peculiarities visible in the shell and the position of the 
ovisacs within the outer or inner gills; these characters are only known in the 
Kuropean, North-American, and some South-American species, the other forms having 
to be intercalated according to the sculpture of the summits, or, in cases where this 
could not be ascertained, by the general resemblance of the shell to that of better- 
known species. Numerous genera are distinguished, but a considerable number of 
species are left under the old name Unio. The arrangement, of course, differs in many 
