442 
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, Pl. 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 Hurystomites Kelloggt, 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, 
Play). 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. 
NauriLus KE.LLocc!, Whitf., of. cit. (Bull. Am. Mus., N. Y., i, 
No.3. Plo xxx: not Pl. xxxi, Migs. 4, 5). 
EvurystTomMitTes KE.LLocci (?), Schréder, of. ct. (Pal. Abh. Dames 
i, Kayseren Witt, 4, ps 20). 
Pl. 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. 
