POLYMESODA. 549 
two from Dunker’s collection (figg. 2, 2a, 6) agree with Fischer and Crosse’s figure, the 
large one (a) with Clessin’s, and one, from Paetel’s collection, is intermediate between 
them in the outlines of the fore part, but in size like d. Our figures 1 and 3 show 
the amount of variation in somewhat younger examples of equal size. 
Very young specimens are quite globose, and they somewhat resemble, externally, 
Corbicula convexa, Desh., according to Prime®. This author mentions also Panama 
as a locality for this species; but, as he gives no information concerning the collector, 
this statement seems to require confirmation. 
Cyrena equilatera, Deshayes, P. Z. S. 1854, p. 20 (C. equilateralis, Deshayes, 
Catal. Conchifera Brit. Mus. ii. p. 255), is quoted by Clessin ® and Fischer and Crosse ® 
as a synonym of P. mexicuna; this shell, however, is from Cayenne, and the 
description, especially ‘testa eequilaterali, lateribus subequalibus,” does not agree at 
all with C. mexicana. Sowerby, in Reeve’s Conch. Icon. xx., Cyrena, t. 19. fig. 114, 
figures for it a very unequilateral shell, with the summits in two-fifths of the length. 
14. Polymesoda inflata. 
Cyrena inflata, Philippi, Zeitschrift f. Malak. 1851, p. 71!; Prime, Monogr. Am. Corbiculade, 
p- 26 (copied from Philippi) *. 
Ovate-triangular, very swollen, rather thin, with irregular concentric strie, dark greenish; summits very 
prominent, rolled-up, decorticated ; ventral margin little arcuated. 
Long. 62, alt. 58, diam. 463 millim. 
Hab. Costa Rica ?. 
According to Philippi, this shell externally resembles Jsocardia cor, L. 
Var. panamensis. 
Cyrena inflata, Deshayes, P. Z. S. 1854, p. 23°; Catal. Conchifera Brit. Mus. ii. p. 260%. 
Cyrena panamensis, Prime, Proc. Acad. Phil. 1860, p. 283°; Monogr. Am. Corbiculade, p. 24‘ ; 
Sowerby, in Reeve’s Conch. Icon. xx., Cyrena, t. 8. fig. 29. 
Seems to differ from P. inflata in having a distinct furrow descending from the summits towards behind 
and below. 
a. Long. 55, alt. 52, diam. 42 millim. (Prime °.) 
S  . (56, ,, 54, 5 ? 5 Vertices in # long. (Sowerby’s figure). 
Hab. Panama 2, 
Var. cordiforms. 
Cyrena cordiformis, Récluz, Journ. de Conch. iv. p. 251, t. 7. fig. 9 (1853) °. 
Cyrena recluzi, Prime, Monogr. Am. Corbiculade, p. 24, fig. 24”. - 
Cyrena maritima (C. B. Adams), Sowerby, in Reeve’s Conch. Icon. xx., Cyrena, t. 8. fig. 30 °°. 
Also with a hinder furrow, but more sharply angulated at the hinder margin below this furrow. | 
a. Long. 74, alt. 74, diam. 55 millim. Vertices in ? long. (Récluz *). 
b 57, , Bh ws Be o i ,, (Sowerby’s figure). 
