Variety ronfadl.! 
BRACHIOPODA. 
449 
Variety conradi N. H. Winchell. 
PLATE XXXriI, FIOS. 37-39. 
1880. Orthis conradi N. H. WiNCiiELL. Eij^hth Annual Report of the Geolo^^ical and Natural 
History Survey of Minnesota, p. 68. 
Original description: "Shell having the shape and size of Orthis disparilis (Con.), 
but with a moderately convex entering valve, with from fifty to sixty fine radiating 
striae on each valve, about half of which disappear before reaching the beak; foramen 
of the larger valve narrow, of the smaller valve triangular; surface with indistinct 
growth-bands, but without evident interradial crenulations; on the center of the 
smaller valve is a flattening that widens from the beak and disappears before reach- 
ing the margin," 
In the upper portion of the Trenton limestone at Minneapolis, Minnesota, and 
Decorah, Iowa, also in the "Lower Blue beds" of Wisconsin at Janesville and Beloit, 
a small form of Orthis, belonging to the 0. perveta group, is constantly met, and to this 
the name 0. conradi has been applied by one of the writers. A similar species has 
been described by Mr. Billings as 0. electra* and was procured in the upper part of 
limestone No. 2 of the Quebec group at Point Levis, Canada. Although these speci- 
mens are from a much lower horizon than the present material, yet the size and 
general external expression are strikingly similar. Of this species Billings writes: 
"The only difierences that can be made out from a comparison with specimens [of 
0. perveta] from Tennessee and the figures given by Hall in the Palaeontology of New 
York are, that in 0. perveta the dorsal valve is more convex than it is in 0. electra, 
and the beak of the ventral valve not so depressed, while at the same time it is more 
extended. At present I have no means of comparing the interior of the two species. 
When such a comparison can be made, should no greater differences be disclosed 
than are afforded by the external characters, I would be disposed to unite the 
two under one name." (Pal. Foss., vol. i, p. 80.) Some northwestern specimens 
have the beak as much depressed as in 0. electra. However, it is usually, if not 
always, more extended than in the latter species, while the dorsal valve seems to be 
more convex. Dr. White** has doubtfully identified 0. electra as occurring at Fish 
Spring, House range, Utah. The greater length of the hinge-line, 16 mm. in these 
specimens, compared with the figures of Canadian examples, the largest of which 
are only half that length, precludes the possibility of their being alike. The char- 
acters by which the northwestern shells can be separated from 0. electra are internal. 
The latter is described as having the dental plates scarcely developed, while no 
* Pal. Foss., vol. 1, p. 79, flg. 72, and p. 217, 1862. 
** Report of U. S, Geog. Surv. west 100th Meridian, vol. Iv, p. 55. 1875. 
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