i<m 



Orthothetes arctostriatus. Hall. ( Fig. 96.) ( Pal. 

 N. Y., Vol. IV., p. 71, PI. IX.) 



Distinguishing Characters. — Hinge line equal to or greater 

 than the width of the shell, .seldom less; sides of the shell 

 rectangular to the hinge line, or curving inward from it ; 

 surface stria? closely arranged. 



— n 



Fig. 96. Orthothetes arctostriatus. Two brachial valves and an enlargement of the sin- 

 face strife (from Hall) . 



■ 





Found in the upper part of the Moscow shales, Sections 2 

 and 3 (rare) ; in the lower Moscow shale, five feet above the 

 Encrinal limestone. Stictopora 

 and Demissa beds, at Section 

 5 ; between one and three feet 

 below the Encrinal limestone, 

 at Section 6 (common); below 

 three feet, at Section 6 (spar- 

 ingly ) ; from seven to twelve 

 feet below the Encrinal lime- 

 stone, at Section 7 (common); I 

 below twelve feet, at Sections 7 I 

 and 8 (sparingly). Also found 

 in the Trilobite beds, at Sec- 

 tion 8 (rare) ; between the Trilo- 

 bite and Strophalosia beds, on 

 the Lake Shore and in Avery's 

 ('reek (common); in the Transi- 

 tion beds, on the Lake Shore 

 (rare). 



Orthothetes per vers us. 



TT-ill ( V\ir 0,7 ^ /Pal "NT Y Vol Fig. 97. Orthothetes perversus. Bra- 



Xldll. ( rig. ^t.) (rdl.i\.I., VOl. chial valve; internal mold of large 



nr ryo -r>i I -v \ brachial valve; pedicle valve (from 



'., p. IZ, ± 1. J A. ) Hall). 





■:>.- 



w 



