816 QUADRULA 
in proportion, shorter and having much fuller, higher beaks 
but there are intermediates, which can hardly be placed. The 
beaks of plicata are generally a little nearer the anterior end 
than those of wndulata. 
Say says: “It was found by Mr. Lesueur in Lake Erie, and 
was communicated by him under the above name.” As there 
is no evidence that Lesueur described the species, and as Say 
was the one to first properly characterize it, I believe that he 
must be credited with it. 
Var. hippopea (Lea). 
Smaller and more delicate than the type; epidermis green- 
ish, greenish-brown or reddish-brown. 
Length 60, height 42, diam. 27 mm. 
Type locality, Lake Erie. Also, Eastern Michigan. 
Unio hippopeus Lea, Pr. Am. Phil. Soc., IV, 1845, p. 163; 
Tr: Am. Phils Soe.;--X,. 1848.-p: (67, pl. a, ie. Obs ve 
1848, p. 41, pl. 1. fig. 1—Kuster, Conch. Cab., 1861, p. 251, 
pl. LXxx1v, fig. 3—Reerve, Conch. Icon., XVI, 1864, pl. x1, 
fig. 40. 
Margaron (Unio) hippopeus Lea, Syn., 1852, p. 21; 1870, p. 
2. 
Quadrula plicata var. hippop@a SIMPSON, Syn., 1900, p. 767. 
Crenodonta plicata ORtTMANN, Ann. Car. Mus., VIII, 1912, p. 
24h. 
Very variable in form and size. Some adult shells are very 
much smaller than the measurements given above. A form of 
plicata left in the St. Lawrence drainage at the close of the 
Glacial Epoch, no doubt, and developed by its environment. 
Ortmann, (1. c.), says, “this species has been misunderstood 
hitherto. ‘The type locality of plicata is Lake Erie, and thus 
the only known Crenodonta from Lake Erie should bear this 
name, but this is the form called hippopea by Lea. The pli- 
cata of authors should be Cr. peruviana (Lamarck).” 
He also says that “this is undoubtedly only a local race of 
undulata.” If this is correct, plicata Say would take precedence 
over undulata Bar. as the specific name for that species. 
