PART I CHAZYAN AND RELATED BRACHIOPODS—COOPER 679 
middle when present, usually low and obscure but more frequently not developed. 
Flanks inflated and with steep lateral slopes. Median ridge moderately strongly 
developed. 
Measurements in mm.— 
Length Width Thickness 
Fiypotype’ (11724208) 5. 2. POR Pa 6.4 6.6 4.6 
is Crizeaeb®.). tonihh. iG. os oe 6.5 6.2 4.2 
¥ Crag2age iti oi-saseeot Ie eee 6.6 6.4 4.3 
f CUA, «at Hcy Sees erent uaa 6.7 6.0 4.2 
- CRASS Gs ssh anciia ss Gate eh Ree 5.8 6.0 a7 
Types—Lectotype: A.M.N.H. 714/1,2a, large imperfect specimen ; paratype: 
714/1,2b, small perfect specimen; figured hypotype: 117242e; measured hypo- 
types: 117242a-c, 1232098a,b. 
Horizon and locality.—Rockland formation (Napanee member) in New York: 
Just west of the bridge over Mill Creek in the city of Lowville, Lowville (15’) 
Quadrangle ; on the west side of New York Highway 12 at its crossing of Sugar 
River, about 4 miles south of Port Leyden, Port Leyden (15’) Quadrangle. 
Discussion.—This species is recognized by its large size, shallow sulcus, and 
moderately strong costae on the margins. It resembles P. profwnda Cooper but 
differs in having a less deep sulcus and a less narrow fold. It also suggests 
P. nicolleti but differs in not having a strong sulcus in the fold of the pedicle 
valve and in not having the strong development of the fold within the sulcus, 
which is so prominent in the Minnesota species. It is also close to P. superba, but 
that species has a short but prominent fold in its sulcus. The Missouri species 
also has fuller and more convex flanks. See discussion of genus above for selec- 
tion of type specimen. 
PROTOZYGA LOEBLICHI Cooper, new species 
Plate 140, C, figures 17-21 
Shell small, subpentagonal to longitudinally elliptical in outline; beak obtuse; 
sides broadly rounded; anterior margin subnasute. Surface smooth in the pos- 
terior two-thirds, marked on the margins by obscure costae, I or 2 of which 
appear on the flanks. 
Pedicle valve evenly and gently convex in lateral profile and with the great- 
est convexity located at about the middle. Beak incurved but not resting on the 
umbo of the brachial valve which is gently convex ; median region inflated ; sulcus 
bounded by 2 narrowly rounded costae, sulcus originating at about the middle 
and extending to the anterior margin; flanks concave and with steep slopes. 
Brachial valve moderately and evenly convex in lateral profile and with the 
maximum curvature near the middle. Anterior profile broadly convex. Umbonal 
region gently convex, median portion of valve somewhat inflated. Fold origi- 
nating in the anterior third, low and narrow, flattened on top and set off by 2 
oblique, shallow grooves. Flanks convex and with moderate slopes. 
