40 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I48 



shell attached to some object that kept it suspended above the sea floor. 

 Assigned species. — The following species are assigned to Atribonium 

 (age and occurrence listed for those not discussed further) : 



A. simatum n. sp. (Type species) 



Seminula bisinuata Rowley 1900, Lower Mississippian, Missouri 



A. cooper orum n. sp. 



Rhynchonella gainesi Nettelroth 1889, Middle Devonian, Kentucky, Indi- 

 ana 



Rhynchonella gainesi cassensis Kindle 1901, Middle Devonian, Indiana 



Hypothyris gregeri E. B. Branson 1923 



Stenoscisma halli Fagerstrom 1961 



S. illinoisensis Cooper 1945, Middle Devonian, Illinois 



Pugnax kemahani Whiteaves 1898 



Camarophoria nora Belanski 1928, Upper Devonian, Iowa 



Camay ophoria obesa Clark, of Shatv, 1962, only (not Clark, 1917), Lower 

 Mississippian, Montana 



Camarophoria paupera Belanski 1928 



C. perplexa Belanski 1928, Upper Devonian, Iowa 



A. pingue n. sp. 



C. planodorsata Belanski 1928, Upper Devonian, Iowa 



C. prolific a Belanski 1928, Upper Devonian, Iowa 



C. retsiaformis Belanski 1928, Upper Devonian, Iowa 



Stenoscisma rhomboidalis Fagerstrom 1961 (not Hall and Clarke) 



A. rostratum n. sp. 



S. savagei Cooper 1945, Middle Devonian, Illinois 



Pugnoides subovata Savage 1921, Middle Devonian, Illinois 



Septalaria (?) subtransuralica Khodalevitch 1961, Lower Devonian, 

 USSR 



A. succiduum n. sp. 



Pugnoides szvallovi E. B. Branson 1923, Middle Devonian, Missouri 



Rhynchonella transuralica Tschernyschev 1893, Lower Devonian, USSR 



Stenoscisma uniplicata Shaw 1962, Lower Mississippian, Montana 



(?) Camarophoria walteri E. B. Branson 1938, Lower Mississippian, Mis- 

 souri 



ATRIBONIUM SIMATUM Grant n. sp. 



Plate 1, figs. 1-12; figures 4, 5, 6 



Shell small, flatly biconvex; outline subtrigonal with length and 

 width nearly equal, widest near anterior ; commissure uniplicate, fold 

 low, broad, flat, expressed on surface of brachial valve as low flat 

 ridge beginning to stand above flanks about 5 mm. anterior to brachial 

 beak; sulcus shallow, broad, beginning 5-7 mm. anterior to pedicle 

 beak ; costae low rounded, simple, beginning 3-5 mm. anterior to beaks, 

 numbering four to seven on fold, one fewer in sulcus, three to six on 

 each flank ; anterior margin flattened or slightly emarginate ; growth 

 lines fine, closely spaced ; growth laminae weak, irregularly and widely 

 spaced. 



