THE NAIADES OF MISSOURI 269 
outer, the whole pad-like; gills large, inner semi-circular, free 
from the abdominal sac or united with it; branchial opening 
large with many smalJ, papillae; anal with well developed papil- 
lae.”” (Simpson. 
SHELL CHARACTERS. 
EXTERNAL STRUCTURES:—Shell sub-elliptical inflated, thin; 
disk smooth; beaks somewhat full with distinct beak sculpture 
consisting of concentric ridges upcurved behind; epidermis dark 
brown, polished, sometimes rayed; hinge-teeth lacking, or merest 
rudiments, scars shallow; nacre bluish white. 
Dr. Ortmann considers this genus pratically an Anodon with 
concentric beak sculpture and as a good connecting link for Ano- 
donia and Alasmidonta. ‘The only species of this genus, ferussaci- 
anus, is only represented along the Mississippi of this state where 
it is a rare shell. Unfortunately the soft parts, have not been 
secured for description. The glochidia of the species and sub- 
species (subcylindricus) of this genus have the same shape and 
measure 0.32 and 0.33mm. respectively—height and length being 
equal. 
Anodontoides ferussacianus (Lea). 
(‘‘Ferussac’s Shell.’’) 
Pl. III, Figs, 7a—8a. 
1834—Anodonta ferussaciana Lea, Tr. Am. Phil. Soc. V, p. 45, pl. 
WL figs 15: 
1898—Anodontoides ferussacianus (Lea) Baker, Moll. Chicago, 
tet e7/ 2.) Die lbs te TO IV, wie nae 
ANIMAL CHARACTERS. 
According to Dr. Ortmann (1912b, p. 294) the anatomy of 
this species is essentially that of Anodonta and differs only in the 
shorter mantle connection between the anal and supra-anal and 
in the anal being distinctly papillose. he glochidia (Ortmann 
1811b, pl. 89, fig. 12) are described as rather small (0.320 x 0.320 
mm.) for the subfamily, subtriangular and spined. 
SHELL CHARACTERS. 
EXTERNAL STRUCTURES:—Shell subelliptical, thin, inflated, 
medium in size, post-umbonal ridge, rather faint; compressed 
with distinct, regular, concentric ridges bent up behind and api- 
culated at the apices; epidermis brownish to bluish-green, some- 
