﻿504 AKASMIDONTA 



Margaritana ( .Uasmodouta) ctowahotsis Cij;ssin, Conch. Cab. 



.■\no., 1875, p. 270, pi. i.xxxi, fifi^s. I, 2. 

 Margaritana rtoii-aluvisls r.i:Ti".i., Conch. Sam.. HI, i8f)0, p. 



Margaritana gcori:ia)w Ij-:\, I'r. .Ac. Nat. Sci. I'liila., Ill, 1859, 



p. 280. 

 Margaron (Margaritana) gcorgia)ia Lf,.\, Syn., 1870, p. 68. 

 Alasinidonta georgiana Simpson, Syn.. upo. p. 670. 

 .llasniodonta iniprcssa .Ax'rHONY, Am. Jl. Conch.. I. 1865. j). 



157. pi. XII. fig. 4. '' 



Lea has three specimens in his collection, which he calls 

 Margaritana georgiana. '^I'he type and a xonns^ shell are no 

 doubt the same thin;;, but the best preserved shell is. T feel 

 sure, a younq- Syniphynota quadrata. It has decidedly and 

 sharply doubly-looped beak sculpture and better developed 

 teeth than the others. The two specimens of georgiana have 

 l)adly eroded beaks, but by a careful examination with a glass 

 T can make out that their .sculpture is coarse, nearlv straight 

 ridges. Their teeth consist of a single rounded knob in each 

 valve ; the laterals are wanting. 



Subgenus Rit.ifkra Simpson. 1900. 



Rn gif era SiursoK, Syn.. 190G, p. 670. 



Shell elongated, rhomboid, inflated, surface brilliantly paint- 

 ed with radiations, which often break into a dappled or splash- 

 ed pattern of color ; posterior slope slightly corrugated ; teeth 

 very imperfect ; laterals wanting. 



Animal with a thick, smooth, pad-like marsupium. Mantle 

 with square spots behind. 



Type, Alasmodonta niarginata Say. 



Al.XSMIDONTA MARGIN ATA Say. 



Shell medium to rather large, long rhomboid, nearly or quite 

 equilateral, subsolid to solid, subinflated ; beaks ver\- full, high, 

 sculptured with a few strong corrugations, which show a ten- 

 dency to be doubly looped ; posterior ridge very high and 

 angled, ending behind in a point at the base of the shell, behind 



