40 
BULLETIN OF THE LABORATORIES 
front of the middle ; concentric striae or folds appear near the front; 
hinge plates sub-parallel, over one-seventh the length of the valves. 
Length to width about as seven to eight. Width 24 mm, height 20 
mm; (21-17; 18-17; 21-18; 18-1 5 ; 23-20. ) 
Dorsal valve more nearly quadrate or sub-circular ; beak short 
and incurved ; casts showing a strong median plate within ; antero-lat- 
eral outline semi-circular, postero lateral angle very obtuse, mesial fold 
inconspicuous, with four or five plicae, lateral areas with four to six 
plicae. Length to width as 4-5. 
The specimens vary in many respects, but in no specimens were 
the mesial plic^ more than four or fi ve, there being three in the sinus 
and four on the fold in normal adults. Two varieties exist side by 
side, differing only in the number of j)licae. 
The second agrees very closely with R. s ippho in some of its va- 
rieties. 
This species belongs in the sandy layers or flags about 40 feet 
below congl, I, where it is abundant. The Granville specimens are 
said by Prof. Winchell to be typical. This is No. 1313, of our Mu- 
seum Register and has now for the first time been described in full. 
Our own belief is that all of the closely allied forms belonging in this 
section of the genus are conditions of a single species — R. sappho. 
Rhynchonellcb sappho, Hall. 
(Plate V, Fig. i; Plate VII, Fig. 25.) 
Of large size, agreeing in outline with R. sageria?ia, but with more 
numerous plicre, there being generally five in the sinus and six on 
either side. It is possible to duplicate the Hamilton forms exactly 
from our collection. 
Found in the free-stone of middle Waverly, and also in free-stones 
from a horizon 60 feet above congl. II, that is in the upper Waverly. 
Some of the varieties of this type resemble R. cooperensis, per- 
fectly. 
Rhyackonella inarshallensis, Win. 
This species is recognized by the ventricose, flattened dorsal valve 
