PART I CHAZYAN AND RELATED BRACHIOPODS—COOPER 429 
Types.—Holotype: 116993; figured paratype: 110459. 
Horizon and locality—Bromide formation (Mountain Lake member—Val- 
courea transversa bed) in Oklahoma: In NE} sec. 1, T. 2 S., R. 2 W., 3 miles 
east of Pooleville ; on Spring Creek in sec. 17, T. 2 S., R. 1 W., Murray County. 
Discussion.—This species differs from all other described forms in the strength 
of the pedicle fold and the deep brachial sulcus. 
Genus CAMPYLORTHIS Ulrich and Cooper, 1942 
Campylorthis ULtricH and Cooper, Journ. Paleont., vol. 16, No. 5, p. 621, 1942. 
Shells wider than long, cardinal extremities varying from alate to obtusely 
rounded. Lateral profile convexi-concave to unequally biconvex, the brachial 
valve always the deeper. Anterior commissure varying from rectimarginate to 
uniplicate. Interareas subequal in length, pedicle one generally apsacline ; brachial 
interarea orthocline to anacline and usually extended posterior to the pedicle 
beak. Surface multicostellate, costellae of unequal size; impunctate. 
Pedicle valve with musculature of Dinorthis consisting of elongate, anteriorly 
widening, and divergent diductor scars, moderately strong adjustor impressions 
at the base of the dental plates, and small adductor field bisected by a low median 
ridge. Muscle area square to elongate rectangular in outline. Teeth small but 
with large fossettes ; dental plates short, stout, and receding, defining small umbo- 
nal cavities. Pallial markings as in Dinorthis. Delthyrium covered. 
Brachial cardinalia as in Dinorthidae; brachiophores short, rodlike, supported 
by excess shell deposited on their inner surface. Cardinal process with short 
shaft and narrow crenulate myophore in the young but with swollen and tri- 
angular myophore in old specimens. Median ridge short, adductor field small. 
Genotype.—Strophomena deflecta Conrad=Campylorthis deflecta (Conrad), 
Proc. Acad. Nat. Sci. Philadelphia, vol. 1, p. 332, 1843. 
Discussion—Campylorthis most nearly resembles Multicostella and possesses 
a similar pedicle muscle arrangement and pallial marks but differs in profile. 
Multicostella is biconvex in lateral profile, but Campylorthis has the pedicle 
valve concave in the anterior half or two-thirds. In some individuals this con- 
cavity is not strongly marked and differentiation from Multicostella is difficult. 
The type species of Campylorthis was long ago assigned to the genus Val- 
courea, and the common presence of a pseudodeltidium in the two genera made 
this similarity striking. Nevertheless, an important difference in the cardinal 
process of the two may be noted. That of Valcourea possesses a high median 
ridge rising above the myophore, but the cardinal process of Campylorthis is 
marked by no such ridge and the structure is like that of Dinorthis with a 
crenulate myophore. 
Campylorthis is also similar to Chaulistomella and differs from it only in the 
possession of a pseudodeltidium. When Campylorthis was first proposed, the 
name included the shells now referred to Chaulistomella, It seemed advisable to 
separate the two, however, because true Campylorthis with the pseudodeltidium 
seems to be confined to the Mississippi Valley region. Chaulistomella, some 
