NO. 7 SILICIFIED ORDOVICIAN BRACHIOPODS ROSS AND DUTRO 7 



Superfamily SYNTROPHIACEA Schuchert and Cooper, 1931 



Genus CAMERELLA Billings, 1859 



Camerella? sp. 



Plate 1, figures 11-14, 16 



Description. — Unequally biconvex with pedicle valve rostrate and 

 brachial valve less convex ; outline suboval with beak angle about 80° ; 

 surface nearly smooth with about 6 broad costae developed in anterior 

 half of shell; faint, shallow median sulcus in brachial valve. Pedicle 

 interior with small spondylium; because of silicified secondary ma- 

 terial, presence or absence of supporting septum not ascertainable. 

 No brachial interiors obtained. 



Discussion. — The two specimens in our collection have had much 

 of the original surface of the shells removed in some unknown manner. 

 The anterior commissure is distinctly toothed, indicating 6 costae on 

 the brachial valve, all in the median half of the shell. The faint sulcus 

 in the brachial valve is a feature suggesting pentamerid rather than 

 camerellid relationships. Until more and better preserved specimens 

 can be obtained, the correct taxonomic position of this species must be 

 considered indefinite. 



Figured specimens. — USNM 145332, 145333. 



Superfamily RHYNCHONELLACEA Schuchert, 1896 

 Genus RHYNCHOTREMA Hall, 1860 

 Rhynchotremaf sp. 

 Plate 1, figures 1, 3, 5 



Description. — Rhynchonelliform, strongly biconvex, subpentagonal 

 in outline; anterior commissure uniplicate; brachial valve with 10 

 strong angular costae, 4 low costae of equal height on fold and three 

 on each flank ; pedicle sulcus with 3 costae ; imbricate ornamentation 

 suggested, although most of exterior has been removed during silicifi- 

 cation process. Pedicle interior with strong dental plates, indicated by 

 molds in interior filling. Brachial interior with strong median septum, 

 divided hinge plate; no cardinal process seen, although absence may 

 be due to poor preservation. 



Discussion. — Unfortunately, the presence or absence of a cardinal 

 process cannot be demonstrated. Although its apparent absence would 

 suggest assigning this shell to Rostricellula, the ornamentation and 

 lack of supporting plates argue more strongly for tentative assignment 



