30 DR. P. P. CARPENTER ON THE SHELLS OF PANAMA. 



" ill-defined." Teeth scarcely visible. It looks outside like a dead 

 valve of Macoma solidula. 



492. Crassatella gibbosa. Also found at Cape St. Lucas. 



493. Mulinia donaciformis— M. angulata, M. 80. 



494. Mulinia ventricosa=^Mactrella exoleta, M. 78. 



495. Lutraria elegans^=narvella elegans; ascribed by Messrs. 

 H. & A. Adams to Florida (ii. p. 378), from which I have never 



1 seen it. It is a rare, but (under different names) somewhat widely 

 diffused west-tropical shell. Its " analogue" from Florida and Ca- 

 rolina is Raeta canaliculata. 



496. Mactra velata— Standella v. Vide M. 79. The "small 

 variety", is conspecific. 



497. Anatina alta. This valve of Periploma may prove identical 

 with one of the four Gulf species. The spoon is supported under- 

 neath by a linear plate. 



498. Pandora cornuta. It is singular that neither Prof. Adams 

 nor Dr. Gould observed that the peculiar characters of this species 

 are due to a fracture, producing a beak and sinus which are not seen 

 on the lines of growth. The sentences about the "rostriform pro- 

 jection," the "sinus," and the "prominent angle," should therefore 

 be erased from the diagnosis. The hinge-teeth consist of a long 

 sharp tooth, very pointed, in one valve, fitting against a less prominent 

 one in the other ; a slight ligamental tooth in the first valve only ; 

 and a very long, sharp, clavicular tooth in each valve, running near 

 the posterior margin, against the inside umbonal portion of which 

 the ligament is attached. Should it prove identical with P. clavicu- 

 lata, the earliest name (as being given in error) may advantageously 

 be dropped. It is surprising that Messrs. H. & A. Adams have not 

 divided the old Lamarckian genus even into subgenera. 



499. Potamomya aqualis. 500. P. inflata. 501. P. trigonalis. 

 These three forms of Azara differ in outline, but not more than do 

 some other species of Corbulids and such shells as Trigona radiata. 

 The teeth, pallial lines, and general characters are the same in each. 

 The first two I should consider certainly identical ; and a large series 

 of specimens would probably graduate to the third. 



502. Corbula bicarinata, M. 30. 



503. Corbula biradiata, M. 31. 



504. Corbula obesa. Stet. 



505. Corbula ovulate, M. 33. 



50(5. Corbula rubra. A young orange-tinted specimen of C. bi- 

 radiata, No. 503. The "broad flexure" is an accidental growth, 

 not shown in the lines of growth of an earlier stage, 



507. Corbula tenuis. Stet. 



508. Corbula, sp. ind. a. A very small angular valve, with sharp 

 concentric ridges. It may belong to C. pustulosa, M. 32. 



204 



