42 
BULLETIN OF THE LABORATORIES 
3 . Schizodus wheeleri, Swallow. 
(Plate III, Fig. 15.) 
This species is identified beyond question and is recognized by 
the great prolongation of its posterior side. The beaks are prominent' 
and situated over one-quarter the length of the shell from the anterior 
margin. The anterior part of the shell is moderately convex, while 
that posterior to the sharply defined ambonal ridge is greatly com- 
pressed. The lower margin is very long and evenly convex, termi- 
nating posteriorly in a prominent acute angle; posterior margin ob- 
liquely truncate; dorsal margin deflected posteriorly. Length, 1.20 ; 
height, .80. Surface marked by very fine concentric lines. 
4. Schizodus cuueatiis, Meek. (?) 
(Plate IV, Fig. 23.) 
It is very strange that the original localities of this species have 
yielded us four species besides, but no typical example of that one. 
The fragment drawn is referred here only because it indicates a spe- 
cies produced posteriorly somewhat and different from S. wheeleri. 
I am inclined to believe that S. cuneatus is not a valid species. 
5. Schizod^US CZtrtuS, Meek and Werthon. (?) 
A single specimen, showing parts of both valves, agrees most 
nearly with this species, but is more like a form figured by Meek, U. 
S. Geol. Surv. Neb., Plate X, Fig. 13d. This he says is probably a 
different species. In S. curtiLS the lower margin is straitened in front 
of the umbonal ridge, in this the regular curve is continued. S. ciirtus 
is so variable that it is not impossible that our species is identical. 
6 . Schizodus {?) spelhnani, sp. n. 
(Plate III, Fig. 14.) 
. A very perfect left valve collected by Mr. Spellman, forms the 
basis of this description. The shell is larger than either of the above, 
but falls short of the maxiiHum of S. cuneatus, which it somewhat re- 
sembles. The margin valve is sub-elliptical, and moderately and 
evenly rounded; ventral margin forming a perfect semi-ellipse ; poste- 
rior side long, posterior margin rounded, beaks moderately prominent, 
