548 MOLLUSCA. 
Hab. Nortu AMEriIca }, 
? CENTRAL AMERICA 4. 
Hanley says that this species is intermediate between P. carolinensis and P. radiata, 
having the membranous wrinkles of the former, the general outlines of the latter. 
Prime * “could not identify it,” but states ‘Central America (cabinet of Hanley) ” ; 
if this statement is correct, Hanley must have obtained information as to locality after 
his description was published. 
12. Polymesoda angulata. 
Cyrena angulata, Deshayes, P. Z. S. 1854, p. 221; Catal. Conchifera Brit. Mus. 11. p. 259’. 
Cyrena tumida, Prime, Monogr. Am. Corbiculade, p. 26 (1865) °. 
Long. 34, alt. 30, diam. 20 millim. 
Hab. Centra America, without nearer indication of locality (Cuming °). 
Prime? says that the name angulata is preoccupied ; he does not, however, mention 
any other species of this name in his ‘Catalogue of the Recent and Fossil Species of 
Cyrena’ (1863), nor in that published in 1869 (Am. Journ. Conch. v.). 
II. Earta, H. & A. Adams. 
i3. Polymesoda mexicana. (Tab. XLII. figg. 1, 1a, 2, 24, 4, 3, 3 a.) 
Cyrena mexicana, Broderip & Sowerby, Zool. Journ. iv. p. 364 (1828-29)*; Hanley, Catal. Rec. 
Bivalv. p. 94°; Carpenter, Cat. Mazatlan Shells, p. 115 (part.)*® ; Mollusks of W. N. America, 
p. 27 (1872)*; Prime, Monogr. Am. Corbiculade, p. 22, fig. 18°; Clessin, in Martini & 
Chemnitz, Syst. Conch.-Cab. ed. 2, Cycladeen, p. 119, t. 22. figg. 8, 4°; Sowerby, in 
Reeve’s Conch. Icon. xx., Cyrena, t. 19. fig. 110"; Fisch. & Crosse, Miss. Scient. Mex., 
Moll. ii. p. 637, t. 70. figg. 7, 7 a, 6°. 
Cyrena floridana (part.), Deshayes, Catal. Conchifera Brit. Mus. ii. p. 257 °. 
Very unequilateral, the hinder part produced, but rounded in its lower half, much swollen, summit very 
prominent, ventral margin nearly straight at the middle. Concentric ridges close together, fine, not 
wrinkled. Inside white, violet only near the anterior and posterior margins. Pallial sinus narrow, much 
ascending. 
a. Long. 513, alt. 41, diam. 28 millim. Vertices in 2 long. 
bh 64, «383, ,, 824, ,, 24 ,, ” 2 4, 
c 5 336, 4 29, 4, 243 ,, ” +, 
d. 39 32, 9 25, ” 22 ” 29 + ” 
a. Specimen from Mazatlan in Dunker’s collection; 6. Measurements given by Broderip and Sowerby, 
reduced to millimetres ; c. Figure given by Clessin; d, by Fischer and Crosse. 
Hab. N.W. Mexico: Mazatlan (Beechey1; Reigen; Deshayes ° 
Dunker). | 
Also in Lower California, at La Paz (Major Rich *). 
3 Forrer, in coll. 
The fore part is more obtuse and descending in Fischer and Crosse’s figure 8, more 
fully rounded in that given by Clessin®, Among the four specimens now before me, 
