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Lituitesmulticostatus, Whitfield (Geo/. Wisconsin, PL xx, Fig. 7). 

 Trocholites multicostatus, Whiteaves ( Geol. Canada, Pal. Foss. , 

 iii, Pt. i, PL vi, Fig. i). PL viii, Figs. 21-23. 



This interesting species of the Niagara fauna is given here in 

 order to show the young neanic stage which was preserved in relief 

 attached to the centre of a mould of the older whorls, Figs. 22, 23, 

 PL viii. The close connection of Discoceras and Trocholites is 

 demonstrated by this drawing. In fact, if separated at this age, the 

 young would have to be placed in that genus. Fig. 2 1 shows the 

 cast of a perfect mould of another specimen of the same species 

 which has reached the ephebic stage. 



Whether this had a dorsal furrow in the umbilical perforation 

 could not be determined. The perforation is certainly very small. 

 Whiteaves' figure shows that the siphuncle is subdorsan in the 

 ephebic stage as it is in the neanic stage described above. 



Systrofihoceras* n. g. 



This genus includes the remarkable series of costated trochoceran 

 and gyroceran forms described by Barrande in his Systeme Silurien, 

 which have the whorls either very slightly in contact, or not touch- 

 ing at any stage, and are devoid of an impressed zone. 



Sy sir ophoc eras (Troch. ) arietinum, rafiax axi&ftingtie, sp. Barrande, 

 have a depressed subtrigonal or subkidney-shaped outline to the 

 whorl with the siphuncle dorsad of the centre, and in many charac- 

 ters are distinct from the others cited below under the name of 

 Peismoceras. These species may have been close-coiled in their 

 younger stages. 



Trochoceras. 



Barrande described this genus in 1848,^ and in the same publi- 

 cation later gave a list of the species J in which the characteristic 

 form, Trochoceras Davidsoni, was mentioned first, and this con- 

 sequently is his type. Hall described the same genus under the 

 same name, but without knowledge of Barrande' s work in the 

 Paleontology of New York,§ but his types are both quite distinct, 

 and do not belong to any genus yet described from Bohemia. 



*Zbarpo(po<z, rolled np. 



f Haidingefs Berichte, iii, p. 266, 1847. 



% Ibid., iv, 1848. 



I Vol. ii, 1852, p. 336. 



