PART. I CHAZYAN AND RELATED BRACHIOPODS—COOPER 823 
Measurements in mm.— 
Brachial Hinge , 
Length length Midwidth width Thickness Height 
HOlotypes iss. Hawes. 4 5.9 5.2 7.3 7.6 1.4? 1.8 
Paratype, (117625). .... ? 73 10.7 10.6 ? ? 
Types.—Holotype: 117626a; figured paratypes: 117625, 117626c, 1176274; 
unfigured paratypes: 117626b,d, 117627b-f. 
Horizon and locality—Tank Hill formation in Nevada: In the ridge just east 
of Monument Canyon, Pioche (1°) Quadrangle; north end of the west side of 
the Ely Spring Range, Highland (15’) Quadrangle. 
Upper Pogonip group in Nevada: In White Pine Range, Hamilton. 
Discussion—No other species of this genus is now known to which this one 
can be compared. 
TERATELASMA Cooper, new genus 
(Greek teras, marvel; elasma, plate) 
Shells small, attaining a length and width of about 4 inch; subquadrate in out- 
line; gently biconvex in lateral profile; anterior commissure narrowly sulcate ; 
surface finely multicostellate. Pseudopunctate. 
Pedicle interior with short, stout flaring dental plates; diductor-adjustor scar 
widely divergent, tear-shaped. Median region narrowly and deeply sulcate. 
Brachial interior with wide and moderately deep notothyrial cavity ; cardinal 
process bilobed ; sockets moderately deep, small, bounded by small, short brachio- 
phores ; notothyrial cavity bounded on each side by a plate inclined to the valve 
floor, lying just anterior to the brachiophore and extending to about the middle; 
median septum club-shaped, originating just anterior to the middle of the noto- 
thyrial cavity and extending to the front margin; median septum expanded and 
elevated at its point of origin in the notothyrial cavity. 
Genotype.—Teratelasma neumant Cooper, new species. 
Discussion.—The interior details of this genus indicate a relationship to Dac- 
tylogomia and the leptaenoids. The exterior is misleading because Teratelasma 
suggests a finely costellate orthid rather than a leptaenoid. The relationship to 
Dactylogoma is clear enough when the shell is examined in detail. Although 
orthoid in appearance, the shell substance of Teratelasma is pseudopunctate. 
Furthermore, the genus has a leptaenoid foramen which can be seen as a small 
plug on the steinkern shown on plate 225, B, figures 5, 6, 7. Internally the rela- 
tionship to Dactylogonia and the leptaenoids is clear in the presence of the bilobed 
cardinal process which shows as two pits in figure 5 referred to above. 
The interior details of this genus are as distinctive as the exterior characters, 
especially in the brachial valve. The cardinalia are characterized by the bilobed 
cardinal process which is small and delicate. The brachial processes are flat, 
oblique blades on each side of the cardinal process. The adductor field is marked 
by ridges similar to those in Dactylogonia but somewhat differently developed. 
The posterolateral adductor ridge is small and not well formed. The inner 2 
ridges are extravagantly developed and may appear as long hollow processes. 
Figure 7 of plate 225, B, shows 2 holes slightly posterior to the middle that 
represent the tubes. The tubular plates can also be seen in figures 10 and II. 
