258 
Aug. F. Foerste 
similar form, Hehertella hellarugosa, has long been known from the 
Trenton, Black River, and Stones River groups of the upper 
Mississippi valley, extending at least as low as the Ridley member 
of the Stones River, in central Kentucky and Tennessee. In 
New York, it occurs as low as the middle of the Chazy. From 
this it will be seen that both lines of descent can be traced back as 
far as the Chazy, and here they are already as strongly differen- 
tiated as at any later time. For the group typified by Hebert- 
ella insculpta, the name Glyptorthis is proposed. In both groups, 
there are forms in which the median part of the brachial valve 
is more or less strongly depressed, so as to produce a median sinus, 
so that the chief distinction of the Hehertella insculpta group is, 
after all, the presence of the concentric lamellose lines of growth, 
combined with a shell form which otherwise agrees with that of 
Hehertella. 
Lamellose lines of growth occur also in species of Eridorthis, 
but in the latter group there is a tendency toward a fasciculate 
implantation of additional radiating plications, and the brachial 
valve, in its initial stages, begins with a median groove between 
two primary depressions, often distinct for a distance of 4 or 5 mm. 
from the beak, while the anterior half of the shell is marked by a 
low median fold involving the two median primary plications and 
4, 5, or 6 additional implanted plications belonging to the same 
fascicles. The corresponding parts of the pedicel valve are 
marked anteriorly by a low median sinus, involving the median 
fascicle and the first major intercalated fascicle on each side. 
In addition to Hehertella insculpta and Hehertella hellarugosa, 
the Glyptorthis group includes the species figured, but not de- 
scribed by Emmons, under the name Orthis crispata, in his report 
on the Geology of New York, published in 1842. It is possible 
that Orthis nisis, and Orthis rugaeplicata, both described by Hall 
and Whitfield from the Louisville limestone at Louisville, Ken- 
tucky, and figured in the Twenty-seventh Report of the New York 
State Museum, in 1875, belong to the same group. 
5. Glyptorthis crispata, Emmons 
{Plate III, Fig. 9.) 
In the Final Report on the Geology of New York, Part II, pub- 
lished in 1842, Emmons figured a form as Orthis crispata, and 
states that it is associated with a form of Dalmanella, which he 
