NO. 2 BRACHIOPOD SUPERFAMILY STENOSCISMATACEA GRANT 151 



troughs present in some individuals, crossing floor of valve just ante- 

 rior to end of median septum ; muscle marks in spondylium weak. 



Brachial valve interior with broadly triangular hinge plate, apex 

 thickened to form cardinal process which is a single small node in 

 young individuals, becoming greatly thickened and binodose in adults, 

 with surface textured for muscle attachment; hinge sockets elongate, 

 narrow, finely denticulate, laterally bounding anterior one third of 

 hinge plate ; crural bases fused to hinge plate, extending from base of 

 cardinal process to anterior edge of plate, there continuing free as 

 slender crural processes, outwardly bowed and gently curved ven- 

 trally ; median septum high, thin, length increasing with height ; cam- 

 arophorium spoon-shaped, widest just behind anterior end, slightly 

 produced at anterior apex ; intercamarophorial plate somewhat shorter 

 than median septum, forming support between camarophorium and 

 hinge plate, median part of hinge plate may extend forward between 

 crural processes and dip from sides to top of intercamarophorial plate ; 

 space between hinge plate and camarophorium may be filled with cal- 

 lus, burying intercamarophorial plate. Muscle marks weak, elongate, 

 located in camarophorium (see fig. IB). 



Holotype. — Camarophoria venusta GIRTY, G. H., 1909, U.S. Geol. 

 Survey Prof. Paper 58, p. 303, pi. 31, figs. 6-6c (USNM 118557). 



Discussion. — This species illustrates great development of the sto- 

 lidium and of internal features characteristic of Permian species of 

 Stenoscisma. The species attains a maximum size much greater than 

 that of S. schlotheimi (v. Buch) and is more strongly costate. It is 

 slightly smaller than the largest specimens of 5". multicostum Stehli, 

 but the costae are coarser, fewer, normally simple, and the outline is 

 less strongly trigonal. 



The stolidium of S. venustum is broad on both valves, and occupies 

 the anterolateral flanks and the crest of the fold (and trough of sulcus) 

 but is not continuous from the fold to the flanks. Pallial marks are 

 visible on internal surfaces. 



Internal features of S. venustum are typical of Permian species of 

 the genus, with the spondylium deep, the camarophorium large, ven- 

 trally curved, spoon-shaped, and the gonocoels linear, troughlike, ex- 

 tending laterally from the median septum of the pedicle valve. Excep- 

 tionally well preserved silicified specimens from the Glass Mountains, 

 Tex., provided material for study of the interior and for its illustration 

 (fig. 1, 2; pi. 23). Diagrammatic drawings showing the possible 

 courses of the muscles are based on examples of this and other well 

 preserved species from the same area (fig. 1) . 



Occurrence and age. — Leonard Formation (Early Permian), Glass 

 Mountains, Texas. 



