﻿4^0 SVMI'HVNOTA 



The smallest specimen examined (in Mr. Wheeler's collec- 

 tion), measures: lent^tii 33, hei,iL;ht 33. and diam. 23 mm., 

 being almost circular in shape, and looks, externally, very like a 

 >oung', smooth 0. piistiilusa Lea, the oblique folds being only 

 slightly evident in the post-basal region. 



A very large specimen, also in Mr. Wheeler's collection, 

 measures: length 87, height. /^. ami diam. 48 mm. 



The structure of the soft parts agrees entirel) with that of 

 the sul>family Auodontimc, chielly so the mantle edge and the 

 outer marsupial gill. I'nfortunately only sterile females have, 

 as yet, been obtained, but it is hoped and expected that this 

 ■ deficiency will soon Ijc remedied." 



Genus SVMPHVXOTA Lea. 1829. 



Sympliynota Lea, Tr. Am. i*hil. Soc, ill, 1829, p. 424. — Ort- 



MANX, Ann. Car. Mus., \ IH, 1912, p, 280. 

 / Megadomns Svvainson, Tr. on Mai., 1840, p. 266. 

 / Complanaria Swainson, Tr. on Mai., 1840, p. 290. 



Shell elliptic rhomboid, compressed ; beaks low, their sculp- 

 ture consisting of strong bars ; one pseudocardinal in the right 

 valve and two in the left, the hinder somewhat .\-shaped, cut- 

 ting off the hinge plate in the right valve; laterals generally 

 imperfect. 



Animal having the gills semicircular below, inner the larger, 

 free nearly the whole length from the abdominal sac ; mar- 

 supium thick, pad-like, filling the outer gills ; mantle strongly 

 attached at pallial line ; branchial opening papillose ; anal open- 

 ing without papillae. 



Type, Symphynota comprcssa Lea. 



As T have constituted it, this group contains a few com- 

 pressed species of L^niones from the Ignited States with flat- 

 tened, strongly sculptured beaks. The left valve usually has 

 a strong uneven tooth under the beak that is somewhat \- 

 shaped and this fits into the opposite valve cutting off its hinge 

 line. There is another tooth in the front part of the left valve 

 -and one before the beak in the right and the laterals are gen- 



