﻿PI.AGIOLA 313 



Strong inflation at or behind the middle of the base ; posterior 

 point blunt, more elevated than that of the male shell. 



Length (male) 54, height 43, diam. 28 mm. 



Length (female) 50, height 43, diam. 26 mm. 



Length (female) 44. height 41, diam. 32 mm. 



Nicaragua ; Venezuela ? A specimen in the U. S. National 

 Museum from the Morelet collection is marked with the latter 

 locality. 

 Unio cyrcnoides Pmikipim, Zeits. fiir Mai., I\'. 1847, P- 93 ^ 



Abbild., Ill, 1848, p. 49, pi. V, fig. I. — KusTBR, Conch. Cab. 



Unio., 1862, p. 285, pi. xcvi, fig. I. 

 Margaron (Unio) cvrcnoides Lea. Svn.. 18^2, p. 25: 1870. 



p. 38. 

 Plagiola cyrcnoides Simpson, Syn., 1900, p. 606. 

 Unio neiv'conibianns Lra, Pr. Ac. N. Sci. Phila., \'III, 1856. 



p. 103; Obs., VI, 1857, p. 32. pi. XXX, fig. 27; Jl. Ac. N. Sci. 



Phila., Ill, 1858, p. 312. pi. XXX, fig. 27. — von Maj?tens 



Biol. Cent. .\mer.. Moll., 1900, p. 497, pi. xxix, figs, i, i a-h. 

 Margaron (Unio) nei^'conrbianus Lka, Syn., 1870, p. 36. 

 Unio sagrinaliis Sowt-.rbv, Conch. Icon., XVI, 1868, pi. pxvii, 



fig- 345- 

 Unis gabbianiis, \'on Martens, Hio\. Cent. Anner., Moll., 1900, 



pi. xxxix, figs. 5, 50-6. 



More solid and rudely sculptured, lighter colored and short- 

 er than Plagiola inibricata. Von Martens' figures of Unio 

 gabbianus on plate xxxix of the Riologia certainly represent 

 a specimen of cyrcnoides, though his description applies to 

 gabbianus. 



In a female P. cyrcnoides. which was not gravid, the sulcus 

 near the base of the inside of the marsupium was quite deep, 

 in fact the part above it hung over it in a sort of flap, which 

 would no doubt disappear if it was filled with ova. 



Plagiola i m p.ricata ( Morch ) . 



Shell subsolid, rather inflated, suliovate or subelliptical, with 

 a well-developed posterior ridge; beaks moderately full, their 

 sculpture not seen, but apparently much as in P. cyrcnoides , 



