CEPHALOPODA— ORTHOCHOANITES. 5 i 



Guelph of New York, Ohio and Illinois. 



23. 0. procerum Hall. Devonic. 

 Apical angle from 6°-8° ; depth of camerse about equal through- 

 out, being about one half diameter of the shell in the apical and 

 one fifth the diameter in the apertural portion; siphuncle slightly 

 excentric; no organic deposits. 



Schoharie of New York. 



24. 0. pelops Hall. (Fig. 1249.) Devonic. 

 Large, robust, differing from the preceding in somewhat shorter 



camerae, centren siphuncle, slightly moniliform, with an aureola at 

 the point of insertion on the septum; living chamber with slight 

 constriction. 



Schoharie of New York and New Jersey ( ?) ; Onondaga of 

 Ohio and Canada (?). 



25. 0. tentalus Hall. Devonic. 

 Septa more closely arranged and with less concavity than in 



preceding; siphuncular aureola larger and with additional organic 

 deposit. 



Schoharie of New York. 



26. 0. fluctum Hall. Devonic. 

 With unsymmetrically curved sutures, not oblique to axis, and 



siphuncle centren or nearly so. 

 Schoharie of New York. 



27. 0. molestum Hall. Devonic. 

 With rapidly expanding living chamber; straight and horizontal 



sutures about 4 mm. apart in adult; siphuncle near the ventral 

 side; lamellose, subimbricating growth lines with slight ventral 

 curve on the ventran siphuncle. 

 Onondaga of New York and Ohio. 



28. 0. (Protobactrites) stylus Hall. (Fig. 1250.) Devonic. 

 Cylindrical, slender, with long and unconstricted body chamber 



and nearly centren siphuncle. 

 Schoharie of New York. 



29. 0. constrictum Vanuxem. (Fig. 125 1.) Devonic. 

 Apical angle 6° ; section circular ; siphuncle centren ; camerae 



