OF DENISON UNIVERSITY. 
39 
gill. Hinge and beaks not clearly seen. Length of small specimen, 
,55, height, .50 ; larger specimen, .85 by .70. ’ ^ : 
Genus Astartella. , ' 
Astartellci Jfewherryi, Me k. -r 
(Plate IV, Fig’. 33.) 
This species is very abundant and varies in size greatly, but ad- 
heres strictly to the same type. 
Astartella vera, Hall. (??> 
A species about the same size as the last is less abundant, it seems 
to correspond with the form figured in the second voL of Ohio Paleon- 
tology, Plate XIX, Fig. i. It differs in outline from the latter, but 
the shell figured was evidently broken, as shown by the direction of 
the concentric ribs, the posterior wing being broader than represented. 
It differs from A. Newberryi, chiefly in the somewhat coarser stri«. 
Astartella varica, McChesney. 
( Plate IV, Pfig. 31.) 
This species is not very well represented in our collections. It 
attains as great or greater size than A. Newberryi, but is more flattened, 
with only a slight posterior umbonal ridge, but the specimen figured in 
the Ohio Paleontology, was evidently badly flattened, as the umbonal 
ridge is much more distinct than there represented. Several of our 
specimens were in the same state of preservation. 
Genus Microdon, Conrad, 
The reader is referred to the discussion of this genus, in the 13th 
Annual of the Indiana State Geologist. It seems very probable that 
our specimens are generically if not specifically identical with the little 
shells found in the Spergen Hill, Indiana, limestones. 
