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The umbilical perforation is large and the impressed zone is a 

 contact furrow not generated until the whorls come in contact. 



The contact furrow is deeper and the amount of involution 

 slightly greater in the ephebic stage than is usual in Tarphyceras. 

 It has been supposed, from the large specimen described by Whit- 

 field, that this shell was close coiled and involute throughout life. 

 There is, however, one large specimen (Fig. 4, PI. v) in the Wal- 

 cott collection, U. S. National Museum, which has the entire living 

 chamber and part of the septate whorl free. The living chamber 

 is very variable in length. It is shorter than in Tarphyceras in the 

 adult of Eurysiomites Kelloggi, and in the aged specimen referred 

 to above it was very long. The aperture, as figured by Whitfield, 

 has lateral crests which are most prominent opposite the centres of 

 the lateral zones, receding into sinuses on the umbilical zones. 



The sutures may remain throughout life almost straight, with the 

 slightest of lateral lobes and ventral saddles, or they may become 

 quite sinuous, with well-defined lateral lobes and the ventral saddles 

 entire or divided by median lobes. A distinct dorsal lobe makes 

 its appearance in the contact furrow when this is formed and on 

 the gerontic volution this furrow persists as an impressed zone 

 although entirely freed from contact with the inner whorl (Fig. 5, 

 PI. v). It diminishes slowly in depth and breadth, but its per- 

 sistence on the dorsum of this very long free gerontic stage shows 

 that it has acquired a strong hold upon the organization of this 

 specimen. Having no other specimens it cannot be said that this 

 persistence is common to all individuals of the species. 



EURYSTOMITES KELLOGGI. 



Nautilus Kelloggi, Whitf., op. cit. {Bull. Am. Mus., N. Y., i, 



No. 8, PI. xxx ; not PI. xxxi, Figs. 4, 5). 

 Eurystomites Kelloggi (?), Schroder, op. cit. {Pal. Abh. Dames 



et Kayser, v, lift. 4, p. 26). 

 PI. v, Figs. 4, 5. 



The figures of Whitfield give an excellent general representation 

 of this species. The young are, however, slightly costated in the 

 neanic stage and there are at least two distinct forms placed by 

 Whitfield under this name. 



