120 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I48 



Stenoscisma globulina (Phillips) BRANSON, C. C, 1948, Geol. Soc. America 

 Mem. 26, p. 524 (synonymy only). 



Shell small for genus, moderately biconvex to subglobose; outline 

 subelliptical to subpentagonal, length and width nearly equal; com- 

 missure uniplicate ; fold moderately high at anterior but not standing 

 much above flanks, beginning about 4 mm. anterior to brachial beak 

 (proportionately far forward in so small a shell) ; sulcus shallow, 

 hardly depressed below level of flanks ; costae numbering two or three 

 on fold, one fewer in sulcus, one or (more commonly) none on flanks ; 

 growth lines not observed; growth laminae weak, widely spaced; 

 valves meeting nearly perpendicularly at anterior, without trace of 

 stolidium. 



Pedicle valve most strongly convex just anterior to beak region; 

 beak sharp, suberect to slightly incurved ; delthyrium apparently with- 

 out deltidial plates ; foramen not penetrating apex of beak. 



Brachial valve more strongly convex ; greatest convexity near pos- 

 terior, longitudinal convexity lower toward anterior along fold. 



Pedicle valve interior with dental plates forming spondylium, ses- 

 sile in extreme apex, then elevated on low median septum, extending 

 anteriorly about one-third length of valve. 



Brachial valve interior with small hinge plate at posterior; cam- 

 arophorium beginning as slender-sided trough on top of septum in 

 posterior, curving ventrally, extending about one-third length of valve ; 

 intercamarophorial plate not observed, probably present. 



Comparisons. — Coledium globulinum is characterized by its small 

 size, globose shape, few costae, and its camarophorium that begins as 

 a trough, not a knob, in the apex of the valve. It is the smallest known 

 species of the genus, and is much smaller than the other species that 

 occurs in the Permian, C. crassum (Hamlet) from Timor. Its shape is 

 most like that of C. explanatum (McChesney) and C. obesum (Clark), 

 but it is smaller and less strongly costate, especially on the flanks. It 

 also resembles C. bowsheri (Cooper), differing in its smaller size, 

 narrower and less pentagonal outline, and in the presence on some 

 specimens of costae on the flanks. 



Discussion. — The U.S. National Museum has four specimens of 

 C. globulinum (USNM 96284) from the Permian of Tunstall, near 

 Sunderland, England, a locality cited for the species by Davidson 

 (1858). These confirm the suspicion aroused by Davidson's and Phil- 

 lips' (1836) descriptions and illustrations that the species belongs to 

 Coledium. As such, it is one of the youngest known species of the 

 genus: only H. crassum (Hamlet) from the island of Timor also is 

 known from the Permian. 



Davidson (1863, p. 116, p. 268) concluded from examination of 



