NO. 1596. DALMANELDAS OF THE CHEMUNG—WILLIAMS. 55 
DALMANELLA TIOGA Hall, sensu stricto. 
Pikes JOO, iS, Il, Py, Bs, Gb eH, 5 Bs MO, 1% 
(=Orthis tioga HALL in part.) 
In the original description of Orthis tioga the form is defined as 
follows: “Shell transverse, broadly elliptical, about two-thirds as 
long as wide; length of hinge line a little greater than half the width 
of the shell; the extremities rounded into a general curved outline.” ¢ 
Hall’s figs. 20, 22, 29, and 24 on Plate VIII accompanying the de- 
scription represent such a form, and they are regarded as types of 
the species as here restricted. The broadly elliptical form is char- 
acteristic, and the specimens are gently convex but neither gibbous 
nor flat. The median sulcus of the brachial valve is distinct but 
shallow, and the median ridge of the pedicle valve is also distinct 
from beak to front, but it is low and not carinated. The radiating 
surface lines (“striae”) are distinctly fasciculated as is shown on 
our fig. 4, Plate III. 
The cardinal process is rather small and narrow, but in well-pre- 
served molds its subdivision into three longitudinal ridges is evident. 
In dimensions the species is intermediate between the earlier forms 
(D. danbyi, superstes, and leonensis) and the common Chemung 
forms D. edmira, and carinata. 
The specimens in the U. S. Geological Survey collection selected to 
represent this species (see Plate III) measure as follows: 
Jere, Ce IS [ony 1G)s') Teawaay. 
Fig. 4, 12.9 by 19.7 mm. 
Fig. 10, 16 by 25.5 mm. 
Fig. 1, 13.6 by 19.7 mm. 
Fig. 3, 14.9 by 22 mm. 
Bigs 12) 15-4 by 21.5 mm. 
Average, 14.1 by 21.8 mm. 
Hall’s figures on his Plate VIII measure as follows: 
Wig. 20, 14.3 by 21.3 mm. 
Hie, 29, 118 by 27 mm. 
Fig. 22, 20 by 29 mm. 
The molds of an interior and an exterior of a large brachial valve 
of this form from Granville center, Bradford County, Pennsylva- 
nia, 1455 Bt? show the following dimensions: 25.2 by 40 mm. 
Plate ILI, figs. 2 and 5. 
All of the forms mentioned above come from the lower part of the 
Cayuta member of the Chemung formation but above the Dalmanella 
danbyi zone. ‘The species is associated with ). elmira, but D. elmira 
CAP alee Nem Ye lVenl SGuan 59: 
5’U. S. Geological Survey, Bull. 244, p. 104. 
