212 MAZATLAN TNIVALVES 



Genus GADINIA, G-ray. 



Phil Mag. 8f Journ. 1824, p. m-. — Fhil. Eandb. Conch. 



p. 199— ^. ^ A. Ad. Gen. vol. i. p. 463. 

 Mouretia, Sow. Proc. Zool. Sac. 1835, p. 6 : — Zool. Beech. Voy. 



p. 147. 

 Pileopsis and Patella, sp. auct. 



270. Gadinia pentegouiostoma, Soto. 



G. t.plus minusve conicd, sen valde depressa, albd; subcirculari, 

 seu irregulariter varie angulatd ; apiee subcentrali, in adultd 

 detrito, injuniorespirali, anfraotihus planorbiformihus, adver- 

 sum cervicem latei'aliter affixo ; costis plurimis radiantibus, 

 angttstis, rotundatis, valde extantibiis, intersfitiis subcequantibus ; 

 margine costis prodioctis, cavatis, subdJaphanis ; canali minimd, 

 ad marginem hand extante ; cicatrice musculan dextrorsum 

 integro, sinistrorsum irregulariter lobato. Animal cavitatem 

 corroderde. 



Siphonaria pentegoniostoma, So^o. ? ubi. 



Having met with, no description of this shell, the name of 

 wtich is Ukcly to mislead, I have drawn out a diagnosis from 

 a comparison of several hundred specimens. Most of the shells 

 are very irregular in growth, apparently crowding each other 

 and forcing their bodies into augidar shapes : but the normal 

 condition api^ears to be nearly round, with semi-transparent, 

 hollowed, projecting ribs. The muscular scar, on the opposite 

 side from the slit, is irregularly divided into lobes. The mus- 

 cle of attachment appears very strong, the shell being generally 

 broken in removal ; and on the place of adhesion (which is 

 eaten away) is generally seen a black circular ring. Ko very 

 young specimens were found, to compare with those of Siphon- 

 aria : but on the smallest, '23 in length, is just discernible a 

 small planorbiform apex, turned to one side, away from the 

 head ; in this respect agreeing with Siphonaria and differing 

 from Patella. The ribs are of nearly equal size, there being 

 no large one to receive the canal, as in Siphonaria. The shell 

 often begins very conical, and suddenly becomes flat. A 

 regularly grown up sp. measures long. "68, lat. "63, alt. 'IS. 



The largest sp. „ „ "98, „ "88, „ '43. 



A flattened sp. „ „ "67, „ "53, ,, 'IG. 



