520 
‘*493,’’ which has also the characteristic form and markings of 
this genus. ‘This last has no contact furrow, according to Barrande’s 
Fig. 7, even in a late neanic substage, although there isa distinct 
contact furrow in the ephebic stage according to his figure of the 
full-grown shell. 
Melonoceratide. 
Under this title, in Genera of Fossil Cephalopods, 1 included 
a number of genera having special interest in this connection. The 
impressed zone is not present in Melonoceras, which is an arcuate 
form, and in most species of Oonoceras. 
Cranoceras, containing the only apparently arcuate form possess- 
ing a dorsal furrow, belongs to this family and appears to be allied 
to the more closely coiled nautilian forms Nedyceras. All of these 
’ forms have subtrigonal whorls, with siphuncle ventrad of the centre. 
The resemblance of Estonioceras and Remeléceras have led me to 
place them also under the same family name. 
Et stonioceras. 
This genus was described by Notling,* and separated from 
Lituites, which it only remotely resembles in having some of the 
volutions free. 
Schréder has more fully described the genus} than any other 
author, and given all the European species with great care, but has, 
in my opinion, included in it some forms with quadragonal whorls 
and siphuncles in different positions which should be separated as 
Remelé has done under the name of Facilituites. 
Estonioceras has a nepionic stage with a large umbilical perfora- 
tion like that of other species of the same phylum. The apex 
itself, the ananepionic substage, is remarkably large and grows with 
extreme rapidity in its transverse diameters, showing the tendency 
to form a broad, digonal whorl, and is cap-shaped when seen from 
the side as in Trocholites and Ophidioceras and very large in all its 
diameters. The sutures of the meta- and paranepionic substages 
throughout the greater part of the first whorl, as seen in the speci- 
men Fig. 13, Pl. vii, and in Schréder’s figure of apex of Lstonioceras 
emperfecium, Pl. iv, Fig. 5, a-b, reproduced here on PI. vii, Figs. 20 
* Op. cil., Jahrb. d. konig.-preus. geol. Landesan. u. Bergak., 1882. 
+ “Ueber Sil. Ceph.,’’ Pal. Abh., Dames et Kayser, y, hft. 4. 
