529 



Orthis. 



valve the impression is ovate, bilobed. Tlie margins are dis- 

 tinctly lobed in four divisions. The greater portion of the 

 specimens observed have a diameter of from 20 to 25 mm. 

 This species may be distinguished from Orthis impressa^ of this 

 formation, by its smaller size and its more circular outline; 

 from Orthis tioga^ by its more circular outline, less conspicuous 

 sinus and elevation, and ovate muscular impression. Forma- 

 tion and localities, Chemung group, Sullivan township, Tioga 

 county ; P. and E. Kailroad, between Ludlow and Wetmore, 

 and Kinzua creek near west line of McKean county ; and at 

 various other localities in Pennsylvania. — VIII g. — Note. 

 In KandalPs collections at Warren, Pa., specimens 9520 A, 

 9522, 9523, 9524, wrongly labelled Orthis meohelini. — Chemung- 

 CatsUll, VIII-IX. 



Orthis perelegans. Hall, Pal. N. Y. Vol. 3, 1859, plate 13, 



VI. ,.-^^ liyjy ^^^^. 'Qc fig- 9 a, ventral, and 10 b, 



'/^mwm^^k^^^ ^mm p:f^^^ dorsal valve. lower Hel- 



(ier berg lormation. — in 

 Pennsylvania, (Cat. 00, p. 

 234), specimens 601-18, and 

 1^. ^''''^^....u^ (four) in collections 



at and near Orbisonia, Huntingdon Co., Pa. from Lower Hel- 

 derherg^ VI — Dr. Barrett's collections at Port Jervis, from 

 Stormville shales. Go, p. 132. — VI 



Orthis pervetus, Conrad. Proc. Acad. Nat. Sci. Phila. Vol. 



5^ & c d e f 



GcoiSsi/ Can>^~\^ 



1, 1843. Blaoh river Trenton formations^ II c. — Geology Can- 

 ada, 1863, page 130, figs. 57 a^ J, <?, d^ e, different views of two 

 s eparate specimens from the Canadian Chazy formation., II h, 



Orthis planoconvexa, Hall, Pal. N. Y. Vol. 3, 1859, plate 

 Vl/ 2.a . 3. J, ^^j^.^_ Ca 



