PART I CHAZYAN AND RELATED BRACHIOPODS—COOPER 559 
Suborder SYNTROPHIOIDEA Ulrich and Cooper, 1936 
Superfamily SyNTROPHIACEA Schuchert and Cooper, 1931 
Family SYNTROPHOPSIDAE Ulrich and Cooper, 1936 
Smooth or ribbed Syntrophiacea having long, convergent, subparallel septa in 
the brachial valve. 
Genus RHYSOSTROPHIA Ulrich and Cooper, 1936 
Rhysostrophia Utricu and Cooper, Journ. Paleont., vol. 10, No. 7, p. 630, 1936; Geol. Soc. 
Amer. Special Pap. 13, p. 240, 1938. 
This genus is known from the high “Pogonip” of Nevada where it is repre- 
sented by two species. It is also known from certain boulders in the Mystic 
conglomerate, which have produced two additional species. Its range is now 
extended to Newfoundland where it occurs in the Table Head series. 
RHYSOSTROPHIA ELLIPTICA Ulrich and Cooper 
Rhysostrophia elliptica ULR1IcH and Cooper, Geol. Soc. Amer. Special Pap. 13, p. 240, pl 54C, 
figs. 5, 6, 1938. 
Types——Holotype: 91176c ; paratypes: 91176a,b,d-f ; 92883a,b. 
Horizon and locality—Mystic conglomerate in Stanbridge Township, Quebec, 
Canada: 2.6 miles north and 4 mile east of Mystic, Range 6, Lot 21, and Range 6, 
Lot 20. 
RHYSOSTROPHIA NEVADENSIS Ulrich and Cooper 
Rhysostrophia nevadensis Utricu and Cooper, Journ. Paleont., vol. 10, No. 7, p. 630, 1936; 
Geol. Soc. Amer. Special Pap. 13, p. 241, pl. 54D, figs. 9-11, 13-19; text fig. 10, 1938. 
Types.—Holotype: 91172; paratypes: 92884a-e. 
Horizon and locality—Upper Pogonip group (Rhysostrophia zone) in Ne- 
vada: I mile above the mouth of Ikes Canyon, east side of Toquima Range, 
Roberts Mountains (1°) Quadrangle. 
RHYSOSTROPHIA OCCIDENTALIS Ulrich and Cooper 
Plate 112, B, figures 3-7 
Rhysostrophia occidentalis ULricH and Cooper, Journ. Paleont., vol. 10, No. 7, p .630, 1936; 
Geol. Soc. Amer. Special Pap. 13, p. 242, pl. 54B, figs. 3, 4, 7, 8, 12, 1938. 
Types.—Holotype: 91174; figured hypotype: 117163. 
Horizon and locality Same as preceding. 
RHYSOSTROPHIA TRANSVERSA Ulrich and Cooper 
Plate 109, F, figures 30, 31 
Rhysostrophia transversa ULRicH and Cooper, Journ. Paleont., vol. 10, No. 7, p. 630, 1936; 
Geol. Soc. Amer. Special Pap. 13, p. 242, pl. 54A, figs. 1, 2, 1938. 
Types.—Lectotype: 91175b; paratypes: Q1175a,c. 
Horizon and locality.—Mystic conglomerate in Quebec, Canada: Range 6, 
Lot 20, Stanbridge Township. 
