$84 QUADRULA 
Unio catillus Conrap, Monog., III, 1836, p. 30, pl. xm, fig. 2. 
—Kusterr, Conch. Cab., 1852, p. 64, pl. xv, fig.-2. 
Unio catilis B. H. Wrtcut, Check List, 1888. 
Unio gouldianus Warp, Jay’s Catalogue, 3d ed., 1839, p. 24. 
Unio cuneus. Cat, Tr. Ac. Sci. St. Louis, VII, p. 14. 
In the Transactions of the American Philosophical Society, 
VI, 1838, p. 12, pl. v, fig. 12, Lea described this species, and 
stated that about eighteen months previous Dr. Hildreth had 
sent him a single specimen under the name Unio coccmeus; 
but there is nothing to show that Hildreth had described it. 
In the Monography in 1836, III, p. 20, pl. xin, fig. 1, Conrad 
describes this species under the same name, and also credits it 
to Hildreth, stating that it was in the collection of the Phila- 
delphia Academy of Natural Sciences under that name. ‘The 
species must be credited to Conrad, who first described it, 
though I,ea read his description in 1834. 
This is an exceedingly variable species and difficult to 
diagnose. It is more compressed than solida, the beaks are not 
quite so high, there 1s no such full, median, radial swelling, 
and it does not have a radial depression in front of the poste- 
rior ridge. Yet there are intermediates that I do not believe 
any one can satisfactorily name. ‘This species occasionally 
shows dark rest marks. 
Ortmann, (1. c.), states that in this species only thé outer 
gills are marsupial. 
Var. magnalacustris n. n. 
Shell much smaller than the typical form, subinflated to 
inflated, subsolid; epidermis light reddish-brown, with darker, 
impressed rest marks, subshining. 
Length 49, height 39, diam. 23 mm. 
Length 44, height 30, diam. 24 mm. 
Type locality, St. Lawrence basin at and near Niagara Falls. 
Quadrula coccinea var. paupercula SIMPSON, Syn., 1900, p. 
789. 
In this form the epidermis is almost shining, a light reddish- 
brown and the darker rest marks are decidedly impressed. 
