GUELPH FAUNA IN THE STATE OF NEW YORK 105 



eral tendency is toward a dextral enrolment, and the sinistral forms represent 

 only early variations. It should be noted also that the late Devonic species 

 are all dextral. 



As Professor Hyatt has made no mention of this difference in enrol- 

 ment, it may be inferred that he did not regard it of special significance. 

 He did, however, at one time 1 separate from Trochoceras in its restricted 

 sense the genera Peismoceras and Systrophoceras, basing these divisions 

 principally on the characters of the aperture, position of siph uncle and sec- 

 tion of whorl. From a note in Whiteaves's description of T. d e s p 1 a i n- 

 e n s e, it seems that Hyatt would have referred that species and evidently 

 also T. costatum to his Peismoceras. In Zittel-Eastman's Textbook of 

 Paleontology \ however, he has covered these names again under Sphyrado- 

 ceras, which is here considered a synonym of Trochoceras Barrande, sensu 

 stricto. 



Trochoceras costatum was described as from the Niagaran 

 limestone at Racine and near Milwaukee Wis. In v. 2, Geology of Wis- 

 consin it is only cited by Chamberlin among the species of the Racine 

 limestone, but not among the Guelph forms. 



ANNELIDA 



ooBNutiTEs Schlotheim 



Cornulites arcuatus Conrad 



Plate 4, fig. 1-5 



Cornulites arcuatus Conrad, Acad. Nat. Sci. Jour. 1842. 8: 276, pi. 17, fig. 8 



Three well preserved specimens from the dolomites at Rochester and 

 a greater number from both horizons near Shelby are referable to this 

 species which was described as follows : 



Curved, rapidly attenuate ; the base of each ring contracted, the upper 

 edge angular. 



It is not altogether certain that Cornulites flexuosus Hall 

 (== C. c 1 i n t o n i Hall) from the Clinton, is sufficiently different to permit 



1 Phylogeny of an Acquired Characteristic, p. 500 and 502. 



