104 The America)! (ieohxjist. February, 1«97 
ically more remote, and possibly O. emxicerdia. is more nearly the parent 
tvpe. 
ORTHIS POR RECTA n. sp. 
PI. V, fig. 19 to 24. 
This Or//; is is found in the Triplecia bed (10) near Granger, and near 
Wykoflf, Minnesota, associated with O. corjntleiitaSm'deiion. Sjjecimens 
are not numerous, and perfect ones are few. When crushed fiat they 
might be mistaken for O. eorpulenta in the same condition, or more eas- 
ily for O. emacerdta Hall. The last named has not been found in the 
Triplecia bed, although it must have existed at that period. The "Or//i/.s 
iestudinarut,'^ associated with TelJinomya fecunda Hall, at Scales 
Mound, Illinois, and Dubuque, Iowa, are casts, sometimes with shells, 
which seem to have been fossils transported and deposited as such in 
the lower strata of the Maquoketa formation. And although most of 
these Orthis belong to the species here described, their occurrence and 
association with other species in that bed may not indicate that this 
species lived at that time. 
Shells of (>rthis porrecta n. sp. are about one-fourth, or less, broader 
than long, the lateral and anterior margins are neatly rounded, and the 
greatest breadth is about midway forward, or posterior to that. Young 
specimens are more nearly semi-circular, and old ones circular. The 
ventral valve is moderately convex and has the beak short, and but lit- 
tle curved, although high so that the greatest convexity of the shell is 
near it. The dorsal valve, which is equally convex, is deepest centrally. 
A narrow, shallow median depression on the dorsal valve extends to 
the anterior margin, and the ventral valve has a corresponding, low 
median ridge. The area of the ventral valve is about twice as high as 
that of the dorsal and is divided by the foramen, which is a little nar- 
rower than high. The cardinal process, crura and muscle scars on the 
dorsal valve are all small, and the muscular area of the ventral valve is 
also not large. The outer surface of the shells has angular, smooth 
plications that bi-anch much the same as in O. emaeerata Hall. Con- 
centric lines are few. 
From O. emaeerata Hall, this species can be distinguished by the 
greater convexity of the dorsal valve, by the circular outline and shorter 
hinge, by the smoother, but more angular plications, higher cardinal 
area, and narrower foramen, and by smaller muscle scars. 
ORTHIS FUTILIS n. sp. 
PI. v, fig. 25, 26, 27. 
In the Triplecia bed (10) at Granger and also near Wykoflf and Spring 
Valley, Minnesota, occurr rarely specimens of an Orthis that might, 
from general characters, be taken for umall O. emaeerata. Hall. Simi- 
lar ones occur in the Wykoff bed (1.3 and 14) near Spring Valley, and 
are there associated with O. emaeerata HaU, some of which they closely 
resemble. Neither are there very abundant, so that the general rela- 
tion of the shells is drawn from the characters of a few individuals. 
O. futilh n-sp., are small, thin shells, finely plicated, so that while 
they are much smaller than O. emaeerata H., they still show an ad- 
vanced plication and general outline such as seen only in the most ma- 
