NO. 2 BRACHIOPOD SUPERFAMILY STENOSCISMATACEA GRANT 53 



The range of variation between specimens that Fagerstrom assigned 

 to 5. rhomboidalis and S. halli is well within the limits for other spe- 

 cies of Atribonium, therefore, they are treated here as a single species. 



Table 4. — Measurements of Atribonium halli 



Measurements, in millimeters Fagerstrom's 



USNM No. Length Width Thickness Plate Figure 



549475 c.5.5 5.6 3.5 



549476 6.4 6.2 4.4 



549477 7.6 7.8 4.8 9 48-41 



Occurrence. — Localities 6 and 43 of Fagerstrom (1961), in For- 

 mosa Reef of Detroit River Group in southwestern Ontario. 

 Age. — Early Middle Devonian (Onondaga). 



ATRIBONIUM KERNAHANI (Whiteaves) 



Plate 3, fig. 4 



Pugnax kernahani WHITEAVES, J. F., 1898, Contr. to Canadian Paleont., vol. 



1, pt. 5, No. 7, p. 387-388, text fig. 3. 

 Camarophoria kernahani (Whiteaves) STUMM, E. C, 1942, Journ. Paleont., 



vol. 16, No. 5, p. 556, pi. 84, figs. 25-27. 



Supplementary description. — Shell small for genus, outline sub- 

 trigonal to subpentagonal, profile wedge-shaped; commissure unipli- 

 cate; fold very high, narrow at anterior, standing above flanks only 

 beyond 3-4 mm. from brachial beak ; sulcus deep at anterior, depressed 

 below high and sharp flanks; costae distinct only at anterior, there 

 having sharply rounded crests, beginning 3-5 mm. anterior to beaks, 

 numbering two on fold, one in sulcus, two or three on each flank; 

 growth lines fine, closely and evenly spaced, visible primarily on flat- 

 tened anterior surface ; growth laminae stronger, widely and irregu- 

 larly spaced. 



Pedicle valve flatly convex, with slight swelling in umbonal region, 

 recurvature of anterior flanks on adults, strong longitudinal convexity 

 through sulcus ; beak proportionately long, sharp, nearly straight to 

 suberect ; beak ridges sharp, outlining flattened and compressed areas 

 on each side of beak ; delthyrium small, triangular, partly closed by 

 pair of conjunct deltidial plates, leaving small elongate oval foramen in 

 apical part ; foramen not piercing apex of beak. 



Brachial valve more strongly convex, producing most of wedge- 

 shaped profile ; beak short, somewhat attenuate, apex in pedicle valve ; 

 posterior lateral slopes somewhat pinched, meeting edge of pedicle 

 valve without overlap. 



Pedicle valve interior with dental plates meeting to form spondyl- 



