﻿3o6 TI.AGIOI.A 



paintiiit; and to sonic extent rescnible siicli Central American 

 specimens as /'. cxrcnoidcs and imbricato. 



Rafinesqiie's name dcprcssa. for \\hat is proljably a male of 

 this species, has jirecedence over Lea's name, but it was used 

 previously b\- Lamarck for an Australian Un'w. Rafinesque 

 placed this species in his se""s Obliqnaria and the sub.q:enus 

 Plagiola, but after g'iving- the name Oblujuivia dfprcssa he 

 called it IL depressa in parenthesis. 



Sub<;enus AMVC.DAixtN.MAS h'ischer and Crosse. 1893. 



Amygdalonaias Fischkj^ and CKt>ssE, Miss. Scient. Mex., Moll.^ 



IL 1893, p. 557. 

 Amygdalonajas Ortmann, Ami. Car. Mus.. VIII, 1912, p. 327. 



Shell compressed to inflated, decidedly truncated at tJie pos- 

 terior slope ; surface slightly concentrically sculptured ; poste- 

 rior ridge sharp and well defined ; epidennis shining, some- 

 times wrinkled, looped and painted with a beautiful pattern of 

 broken or arrow-headed rays : area of the beaks flattened off 

 in the direction of the axis of the shell, but not compressed; 

 beak sculpture delicate, somewhat broken and doubly-looped, 

 the anterior loop rounded, the posterior sharp below, the ribs 

 fading out where they cross the posterior ridge ; hinge delicate; 

 pseudocardinals rather compressed, high and ragged ; hinge 

 jilate narrow ; female shell very slightly swollen at post-base. 



Animal having the brancbirc more or less free from the 

 abdominal sac ; marsupium consisting of numerous distinct 

 ovisacs and having a well-marked sulcus extending around it 

 at some distance above its base ; mantle thickened and doubled 

 on its edge, which has dark papillae. 



Type, Unio cognatus Lea. 



Ortmann, (1. c), raises this group to generic rank. 



Group of Plagiola elcgans. 



Shell short, triangular oval, inflated with a very sharp pos- 

 terior ridge extending from the beaks to tlie hinder i)oint of 

 the shell ; male and female shells scarcely distinguishable, both 

 being much expanded in the basal region. 



