550 - MOLLUSCA. 
Hab. 1 CENTRAL AMERICA. 
No locality is indicated for the typical specimen, but Prime ® says that he is satisfied 
on careful inspection that it comes from Central America! 
15. Polymesoda cumingi. 
Cyrena cumingii, Deshayes, P. Z. S. 1854, p. 22°; Catal. Conchifera Brit. Mus. ul. p. 257 ; 
Prime, Monogr. Am. Corbiculade, p. 25° (probably not C. cumingi, Sowerby, in Reeve’s 
Conch. Icon. xx., Cyrena, t. 12. fig. 53). 
Long. 60, alt. 52, diam. 44 millim. 
Hab. CENTRAL America, without nearer indication of locality (Cuming !~°). 
‘The shell figured by Sowerby under this name is much smaller and said to come from 
the Philippines. 
NEOCORBICULA. 
Neocorbicula, Fischer, Manuel de Conch. p. 1092 (1887). 
Three converging cardinal teeth on each valve; anterior and posterior lateral teeth about equally long, 
furrowed transversely. A small pallial sinus. Shell generally of smaller size than that of Cyrena and 
Polymesoda. 
This genus differs from Corbicula, of the Eastern Hemisphere, by the presence of a 
pallial sinus, a character also separating Polymesoda from Cyrena. ‘The lateral teeth 
are serrated in Corbicula and Neocorbicula, and smooth in Cyrena and Polymesoda, one 
of the genera in each case being Eastern and the other American. Neocorbicula is 
represented by several species in South America, ranging from Venezuela to Argentina, 
but is absent from North America and the West Indian Islands; the occurrence of one 
species in Mexico is open to doubt. 
1. Neocorbicula convexa. 
Corbicula convexa, Deshayes, P. Z. S. 1854, p. 842°; Catal. Conchif. Brit. Mus. ii. p. 2317; 
Carpenter, in Report Brit. Assoc. Advance. of Science for 1863, p. 668, =Mollusks of W. 
N. America, p. 154 (1872)°; Prime, Monogr. Am. Corbiculade, p. 3, fig. 1‘; Clessin, 
in Martini & Chemnitz, Syst. Conch.-Cab. ed. 2, Cycladeen, p. 204’; Fischer & Crosse, Miss. 
Scient. Mex., Moll. i. p. 628, t. 70. figg. 8,8 a, b°. 
Corbicula ventricosa, Prime, in litt. (before 1865) *. 
Rounded-triangular, rather swollen, with irregular delicate concentric striv, light green, inside white. Pallial 
sinus small, triangular. 
a. Long. 18, alt. 16, diam. 13 millim. Vertices in 2 long. 
b. ,, 144,,, 14, , 10 ,, » in nearly 3 long. 
a. fumes figure *; 6. Fischer and Crosse’s measurements and figure °, taken from a specimen in Deshayes’s 
collection. 
Hab. *N.W. Mexico: Mazatlan (Prime *’). 
S.W. Mexico: Acapulco, one worn valve (Dr. Newberry ®). 
