PART I CHAZYAN AND RELATED BRACHIOPODS—-COOPER 341 
swollen and protruding posterior to the hinge; interarea curved, approximately 
orthocline. 
Brachial valve having about half the depth of the pedicle valve, gently convex 
in lateral profile and with greatest convexity in the umbonal region; anterior 
profile broadly convex with short and moderately steep slopes and with the 
median region narrowly depressed by the sulcus. Beak small, protruding slightly 
posterior to the posterior margin ; sulcus originating at the beak and extending 
to the anterior margin and widening anteriorly ; anterior margin with a more or 
less marked reentrant where the brachial and pedicle valve sulci meet; areas 
bounding sulcus moderately swollen; posterolateral extremities concave and with 
short, steep slopes. 
Interior not known. 
Measurements in mm.— 
Brachial Hinge Length 
Length length width Width Thickness of frill 
Btvalentyiicr ied) Ao sty <a eral ines wits eich 4.3 3.9 3.8 5.0 2.5 ? 
Paratype (pedicle valve 116856b)... 5.7 ? rs 5.3 7 Be 2.6 0.7? 
4 (brachial valve 116854a).. ? CIA 3.0 2.8 ? I.1 
Types——Holotype: 116855a; figured paratypes: 116854a, 116856b; unfigured 
paratypes: 116854b, 116855b,c, 116856a. 
Horizon and locality—Table Head series in Newfoundland: 4 mile north of 
Belle Burn; south side of Stearing Island, Cow Head; Table Point Cove. 
Discussion—This species is similar to Orthidium bellulum Ulrich and Cooper 
in its proportions and ornamentation but differs in the strong sulci on both valves 
and the greater depth of the pedicle valve in the Newfoundland species. 
ORTHIDIUM GEMMICULUM (Billings) 
Orthis gemmicula Bituincs, Geol. Surv. Canada, Paleozoic fossils, vol. 1, p. 75, fig. 68 (adv. 
sheets, 1862), 1865. 
Orthidium gemmicula (Billings) Hatt and CrarkeE, Pal. New York, vol. 8, pt. 1, pp. 217, 244, 
pl. 7A, figs. 22-25, 1892ULricH and Cooprr, Geol. Soc. Amer. Special Pap. 13, p. 112, 
pl. 16G, figs. 27-35, 1938. 
Hypotypes.—G.S.C. 9070,a,b,d. 
Horizon and locality—Probably late Upper Canadian (limestone No. 2) or 
younger, Lévis, Quebec, Canada. 
Genus TREMATORTHIS Ulrich and Cooper, 1938 
Tremorthis (sic) Utricu and Cooper, Geol. Soc. Amer. Special Pap. 13, p. 112, 1938. 
Trematorthis Coorer, Journ. Washington Acad. Sci., vol. 32, No. 8, p. 230, 1942. 
TREMATORTHIS MASONI Ulrich and Cooper 
Plate 20, A, figures I-15 
Trematorthis masoni Utricn and Cooper, Geol. Soc. Amer. Special Pap. 13, p. 113, pl. 57A, 
figs. I-9, 13, 1938. 
Types.—Lectotype: 95876c; paratypes: 95876a,b,d-i; figured hypotypes: 
116863a,d-g; unfigured hypotypes: 116863b,c. 
