PART I CHAZYAN AND RELATED BRACHIOPODS—COOPER 7i\i 
Genus GONIOTREMA Ulrich and Cooper, 1936 
Plate 209, D, figures 14-22 
Goniotrema ULricH and Cooper, Journ. Paleont., vol. 10, No. 7, p. 626, 1936; Geol. Soc. 
Amer. Special Pap. 13, p. 193, 1938. 
During the present studies and collecting no more specimens of this interest- 
ing brachiopod were found. Cooper visited Ikes Canyon in 1946 in the hope of 
locating more of this species among other brachiopods but failed. A restudy of 
the type specimen confirms the presence of the foramen which is much too regu- 
lar to be a freak of silicification. The muscle scars are long, slender, and di- 
vergent and reminiscent of Sowerbyites, as is the form and profile of the shell, 
but the anterior callosities so characteristic of Sowerbyites are not present. 
The brachial interior is somewhat reminiscent of Sowerbyites, but the septa are 
much more subdued. Restudy of the cardinalia suggests that a mistake in inter- 
pretation of the cardinal process was made owing to the silicification. It is prob- 
able that the cardinal process is a single piece rather than a lobate form, and 
the posterior part of it including the median ridge has been worn off. If this 
interpretation be correct, the cardinal process becomes like that of Sowerbyites 
and the genus should be classified with the Plectambonitacea. 
Type.—Holotype : 92872. 
Horizon and locality. —Upper Pogonip group in Nevada: In Ikes Canyon, 
Toquima Range, Roberts Mountains (1°) Quadrangle. 
PAUCICOSTELLA Cooper, new genus 
(Latin pauculus, few; costa, rib) 
Shells thin, generally wider than long, with the hinge forming the widest part ; 
surface covered by two sets of costellae, a group of strong distant costellae in a 
mat of fine costellae. Faint rugae may mark the posterior margin. Pseudo- 
punctate. 
Pedicle interior with short and rudimentary dental plates and large and wide 
muscle field. Pseudodeltidium short. Brachial interior with delicate cardinalia ; 
flat bladelike brachiophores ; small notothyrial platform; median ridge short and 
thick, not connected conspicuously with notothyrial platform. Cardinal process 
not seen, probably absent. Chilidium thin, strongly arched. 
Genotype.—Paucicostella canadensis Cooper, new species. 
Discussion.—This genus is based on a species whose details are difficult to as- 
certain. The specimens occur as separated valves in a fairly soft granular lime- 
stone. The shells are so thin that the usual method of burning the shell and then 
developing the interior by use of needles failed to produce useful brachial in- 
teriors, but the nature of the dental plates was determined. The interior features 
of the brachial valve recorded above were obtained by etching the exterior of the 
brachial valve with weak acid and interpreting the structures as seen in the wet 
specimen. 
The interior details are suggestive of those of Ptychoglyptus and Glyptam- 
bonites, but the ornamentation sets Paucicostella off from both of those genera. 
