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SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I48 



valves. Branching is such that it produces one pallial line to go through 

 each costal trough (fig. 2). Anterior to the shell margin in the Steno- 

 scismatidae the pallial marks continue to dichotomize, with one or two 

 bifurcations taking place on the stolidia. The pallial pattern was well 

 illustrated by King (1850, pi. 8). 



Function. — The transverse grooves that cross the pedicle valve from 

 the anterior edge of the median septum to the sides of the valve prob- 

 ably seated some portion of the gonads (Williams, 1956, p. 272 et seq.). 

 The body of the brachiopod, and the major portion of the gonads prob- 

 ably occupied the area posterior to the transverse grooves {see Wil- 

 liams, 1956, p. 272 et seq.). 



The shallow vascula that bifurcate several times in their anterior 

 course onto the stolidia are termed pallial marks. Normally, this term 

 refers to irregularities in the mantle edge, but here it is employed in 

 its general sense for shallow branching lines on the interior surfaces of 

 the valves. Those in the Stenoscismatacea may be genital, or perhaps 

 respiratory, but their thinness, symmetrical bifurcation, and extension 

 out onto the stolidia indicate a possible circulatory function. 



Taxonomic importance and evolution. — Pallial marks are clear only 

 on silicified Permian specimens in the Stenoscismatacea, but on them 

 the pattern seems rhynchonelloid. Among Permian species of Steno- 

 scisma they show no significant change, so I consider it unlikely that 



Fig. 2. — Idealized interior of pedicle valve of Stenoscisma, showing transverse 

 grooves at anterior edge of median septum, pallial marks on valve floor and on 

 stolidium, and posterolateral margins where edges of brachial valve overlap. 



