No. 1596. DALMANELLAS OF THE CHEMUNG— WILLIAMS. 39 
Fourth. The hinge is shorter than the greatest width of shell. 
Fifth. The elevated radiating lines (“striae”) are about fourteen 
at the beak and increase to fifty at the front in the smaller species, and 
to nearly twice that number in larger species. They are more or less 
fasciculated. In extreme cases several very fine secondary lines are 
seen lying on the sides of the dominant primary lines of the group. 
Sixth. In the interior of the pedicle valve there is a more or less 
quadrate muscular impression, pointed toward the beak and bilobed 
anteriorly. 
Seventh. The hinge teeth are prominent and continue into a ridge 
about the muscular scar (much as in Schizophoria.) 
Eighth. In the brachial valve the cardinal process is either simple 
or subdivided in larger shells by three, four, or more longitudinal 
furrows. 
Ninth. The crura are proportionately well developed and show 
serrations on their bases facing the cardinal margin. 
Tenth. In size, specimens of this genus vary from less than 10 to 
over 30 mm. in length, and reach a width in some species of 45 to 
50 mm. | 
Comments.—The exterior of the pedicle valve of the Dalmanellas 
is distinguished from the corresponding valves of Schizophoria by 
the carination of the median line of the shell proceeding from a point 
between the place of the muscular scars to the front. Schizophoria 
has a broad sulcus from half way down which becomes stronger and 
wider at the front. 
In the interior of the shell of Schizophoria the muscular scars are 
divided by a strong median septum, which is evident at the posterior 
end of the scars and becomes stronger toward their front ends. It 
continues forward in a shght septum which in extreme cases nearly 
reaches the front margin of the shell. A similar septum divides the 
muscular scars in Dalmanella carinata, but it is shallow at the pos- 
terior end of the scars, widens and becomes stronger anteriorly, and 
at near the front extremity of the muscular scars it suddenly divides 
into two ridges and becomes lost or inconspicuous around the front 
margin of the scars. Between the prongs of this V-shaped anterior 
termination of the median septum the upfolding of the shell begins 
which constitutes the carination along the middle of the exterior of 
the shell, characteristic of all the larger forms of upper Devonian 
Dalmanellas. In the smaller forms the carination is present, but the 
Y-shaped median septum is not strongly developed. 
This character is expressed on Plate VIII, fig. 30, of the original 
illustrations of Orthis carinata.” Fig. 16 of the same plate is drawn 
to represent a narrow depressed line of the same kind in a specimen 
that would otherwise represent a Schizophoria. ‘Typical expressions 
GIP aYl, ING Moy IVs 
