j6 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I48 



suberect to erect ; beak ridges blunt, short ; delthyrium small, wider 

 than long, constricted but not filled by pair of very small, disjunct 

 deltidial plates; foramen not clearly observed, apparently open but 

 small. 



Brachial valve more strongly and evenly convex transversely and 

 longitudinally ; beak blunt, apex within pedicle valve. 



Pedicle valve interior with short spondylium duplex, about one- 

 fourth length of adult valve, normally sessile in apex of valve, with 

 sides converging anteriorly to form median septum elevating anterior 

 part of spondylium ; muscle and other marks not observed. 



Brachial valve interior with camarophorium on high median septum, 

 joined to underside of hinge plate by short intercamarophorial plate ; 

 septum slightly shorter than septum of pedicle valve, crest of camaro- 

 phorium extending farther anterior than trace of septum along floor ; 

 crura extending anteriorly from edge of hinge plate, curving to follow 

 crest of camarophorium. 



Holotype.—XJSNM 142040, plate 5, fig. 9. 



Table 14. — Measurements of Sedenticellula sacra, from Chappel Limestone, Tex. 



Measurements, in millimeters 



Comparisons. — Sedenticellula sacra is characterized by its large 

 adult size, transversely subelliptical to subpentagonal outline, numerous 

 fine costae that begin near the beaks and bifurcate and intercalate 

 anteriorly. It is much larger and more transverse than the type species, 

 5\ Hamburg ensis (Weller), its costae are stronger and more numerous, 

 beak ridges less acute, beak shorter and more strongly curved, and the 



