NO. 2 BRACHIOPOD SUPERFAMILY STENOSCISMATACEA — GRANT 79 



camara in its sulcate rather than uniplicate commissure. Among lower 

 Paleozoic forms, Psilocamara most nearly resembles Atribonium 

 which normally is only weakly costate. Psilocamara differs from that 

 Devonian form in its smoother shell with high arched rather than 

 broad and flat-crested fold and, internally, in its partly sessile spondyl- 

 ium and lack of an intercamarophorial plate. 



Psilocamara is similar externally to Camerisma n. gen., but differs 

 in its thinner shell walls and, most importantly, in its lack of an inter- 

 camarophorial plate between the camarophorium and the underside of 

 the hinge plate in the brachial valve. The relationships of these two 

 genera are discussed further under Camerisma (q.v.) . 



Discussion. — As presently restricted to species lacking an inter- 

 camarophorial plate, Psilocamara contains only its type species, P. 

 renjroarum Cooper. Possibly Levicamera athyriformis Grabeau be- 

 longs to this genus, but inasmuch as only the pedicle valve of that spe- 

 cies is known, presence of an intercamarophorial plate cannot be de- 

 termined. 



Ustritski (1961, p. 48) placed Psilocamara in the synonymy of 

 Levicamera Grabau, stating that Cooper had violated the rule of pri- 

 ority in establishing it. However, the Code of Zoological Nomenclature 

 requires unambiguous designation of the type species as a necessary 

 condition to establishment of a genus after 1930. Cooper (1956a) ar- 

 gued correctly that Grabau (1934) had not met the necessary require- 

 ments, basing Levicamera on a nomen nudum, and that the name was 

 not available. Ustritski himself disregarded the rules of nomenclature 

 by attempting to change the type species of Levicamera to Camaropho- 

 ria pentameroides Tschernyschev (a species now tentatively included 

 with Camerisma n. gen.). His unorthodox interpretation of the rules is 

 illustrated further by his use of the name Camarophoria King, 1844, 

 for Stenoscisma Conrad, 1839, despite clear priority of the latter (Dall, 

 1877; Cooper, 1942). 



PSILOCAMARA RENFROARUM Cooper 



Plate 9, fig. 1-ld; figure 15 



Psilocamara renjroarum COOPER, 1956a, Journ. Paleontology, vol. 30, No. 3, 

 p. 524, pi. 61B, figs. 20-32, text fig. IB, Nos. 4-15. 



Shell small for genus, subglobose ; outline subpentagonal to sub- 

 elliptical, length normally greater than width, greatest width anterior 

 to midlength; anterior commissure strongly uniplicate; fold high, 

 ogival, with crest gently rounded to slightly carinate, gently curved to 

 flanks without break in slope ; sulcus short, shallow, nearly flat, extend- 

 ing as broad tongue around anterior margin, some specimens with 

 barely perceptible median groove corresponding to crest of fold ; other 



