NO. 2 BRACHIOPOD SUPERFAMILY STENOSCISMATACEA GRANT 120, 



gate subtrigonal outline, by its fold that is relatively high at the anterior 

 but does not stand high above flanks (that is, the fold slants anteri- 

 orly), its two or three low rounded costae on the fold, weakly costate 

 flanks, and long, relatively flat camarophorium. It is nearly the same 

 size as C. explanatum (McChesney), but more elongate, less strongly 

 convex, and less strongly costate. It is smaller and more strongly 

 costate than the smooth C. erugatum n. sp. or weakly costate C. torvum 

 n. sp. Its outline it similar to that of C. therum (Walcott), but it at- 

 tains a much smaller maximum size and there is no trace of a stolidium 

 around the anterior commissure. It is not as wide as C. bowsheri 

 (Cooper) and its flanks are costate; it is not as wide, as large, nor 

 as convex as C. undulatum n. sp., and its costae are fewer, beginning 

 much farther forward. It is proportionately narrower than C. evexum 

 n. sp., and more strongly costate. It is similar to C. cestriensis 

 (Snider), but its costae on the fold are lower, the flanks consistently 

 and more strongly costate, the brachial valve less convex, and the 

 camarophorium longitudinally much less strongly curved toward the 

 ventral valve. 



Discussion. — Coledium rhomboidale occupies a morphologic and 

 probably phylogenetic position transitional from Atribonium to Co- 

 ledium. The manner of meeting of the valves at the anterior, and its 

 outline and costation are fairly characteristic for Coledium, so the 

 species is placed in that genus. However, some individuals have a 

 concentration of growth laminae near the anterior margin that pro- 

 duce a rounded rather than sharp anterior surface. This condition 

 recalls Atribonium, but is not as strongly developed as in any species 

 of that genus ; it is only a rounding, rather than a strong geniculation 

 of the two valves. Another link with Atribonium is the rather flat 

 longitudinal curvature of the camarophorium. This structure is some- 

 what long for Coledium, but also longer than normal for Atribonium, 

 apparently peculiar to the species. The form of the camarophorium is 

 considered more important phylogenetically than the manner of meet- 

 ing of the valves, because of the normal tendency in brachiopods for 

 internal features to be more conservative. Therefore, this species 

 probably constitutes a phylogenetic link between the two genera ; it is 

 the earliest known species of Coledium. 



Fagerstrom (1961) identified specimens from the Formosa Lime- 

 stone of Ontario with Camarophoria rhomboidalis Hall and Clarke, 

 originally described from Cass County, Ind. Numerous topotype 

 specimens in the U.S. National Museum collection from Pipe Creek 

 Falls, Cass County, Ind., are comparable in size and form to Hall and 

 Clarke's illustrated specimens. Their median length is about twice that 

 of Fagerstrom's specimens (U.S. National Museum No. 549475, 



