525 
under side or dorsum. The dorsal lobe is not, however, affected 
to the same extent by senile degeneration, and persists, although 
narrower in proportion in the centre of the suture, as may be seen 
in Fig. 17, Pl. vii. . 
‘The siphuncle is propioventran in all the stages observed from 
the ephebic to the anagerontic. 
Remeléceras,* n. g. 
This genus, known at present only by one species, is closely allied 
as regards aspect and the late appearance of a contact furrow to 
Estonioceras. It differs in having a much deeper furrow, a nephri- 
tic instead of a digonal or depressed elliptical form of whorl and in 
the dorsal sutures and apparently also in the extraordinary form of 
annular muscle. 
REMELECERAS IMPRESSUM. PI. viii, Figs. 1-8. 
Loc. (?) 
This extraordinary form is described and figured in this 
memoir on account of its interesting connection with the history of 
the impressed zone, notwithstanding the absence of any informa- 
tion with regard to the locality. The side view, Fig. 1, Pl. viii, 
shows the sutures, which are similar to those of Estonioceras, and 
the impression of what appears to be the annular muscle at the base 
of the living chamber is very distinct. This may be seen on the 
dorsal side, Fig. 3, where the lower line has a deeper and broader 
depression in the cast reaching across the contact furrow. These 
two lines of depression depart from each other widely on the ven- 
tral side, Fig. 2, the outer one forming a broad saddle. They of 
course correspend to raised 1idges on the inner surface of the shell 
of the living chamber and may have been due to abnormal action 
in the secretions along the upper and lower borders of the annular 
muscle. 
The depth of the contact furrow in the full-grown shell near the 
end of the incomplete living chamber was somewhat greater than is 
given in Fig. 4, but only a shade deeper, and is also slightly 
deeper than this beyond the base of this living chamber on the 
septate part of the volution. In younger stages, shown successively 
in Figs. 5-7, with their accompanying sections, Figs. 6-8, this 
furrow diminishes in depth and breadth and almost disappears 
* Dedicated to Remelé, well known for his original observations on fossil Cephalopods, 
