BART T CHAZYAN AND RELATED BRACHIOPODS—COOPER 709 
APATOMORPHA Cooper, new genus 
(Greek apate, deceit; morphe, shape) 
Like Palaeostrophomena internally but having the normal curvature of Rafines- 
quina, i.e., a flat or concave brachial valve. Shells small in the one known species ; 
concavo- to plano-convex with a moderately long apsacline interarea on the pedi- 
cle valve and a shorter hypercline interarea on the brachial valve. Surface multi- 
costellate. Pseudodeltidium and chilidium long and narrowly arched. 
Pedicle interior with small teeth consisting of an outer tooth and an inner ac- 
cessory dental process produced on the inside of the delthyrial cavity. Delthyrial 
cavity moderately deep; false dental plates extended anteriorly as a ridge on the 
outside of the muscle field. Muscle field fairly large; adjustor scars small, lo- 
cated at the inside base of the false dental plates. Diductor impressions elongate ; 
adductor area small, situated on and beside a low ridge at the very posterior of 
the delthyrial chamber. Area between diductors and in front of adductors, stri- 
ated and roughened. Pallial sinuses strongly impressed ; vascula media wide and 
short, consisting of two depressed channels separated by a low ridge; vascula 
media bifurcating and sending one branch posterolaterally around the sub- 
reniform ovarian impression. The other branch extends anteromedially. 
Brachial interior with a low median ridge most elevated at its anterior end and 
extending for more than half the length of the valve. Brachial processes short 
and stout, orthoid ; cardinal process with thickened shaft cemented to notothyrial 
platform. myophore surface with three ridges, the median ridge forming a high 
thin septum ; the lateral ridges are lower and are given off from the ends of the 
chilidium. Adductor field small, located posterior to the highest part of the 
median ridge; anterior adductor impressions the larger and located inside the 
posterior scars. Pallial trunks with two major branches originating at the inside 
ends of the anterior adductors and running parallel to the median ridge to its 
end where they bifurcate. A second branch originates at the place of division 
between the posterior and anterior adductors and extends anterolaterally for 
some distance then bifurcates sending one branch posteriorly and the other 
anterolaterally. 
Genotype.—Rafinesquina pulchella Raymond=Apatomorpha pulchella (Ray- 
mond). (See below for reference.) 
APATOMORPHA PULCHELLA (Raymond) 
Plate 166, A, figures I-20 
Rafinesquina pulchella RAyMonp, Bull. Mus. Comp. Zool., Harvard Coll., vol. 68, No. 6, 
p. 206, pl. 3, fig. 10, 1928. 
Shell rafinesquinoid in plan and profile ; moderately thick-shelled ; hinge form- 
ing widest part ; cardinal extremities nearly rectangular to acute. Lateral margins 
gently convex; anterior margin broadly to narrowly rounded. Anterior com- 
missure rectimarginate. Surface multicostellate; costellae distant, narrowly 
rounded and appearing in 4 generations. At the front margin of a specimen 
