622 
PLATE IV. 
Fig. 1 Baculites compressus, enlarged sutures after Brown, see PI. iii.* 
Fig. 2. Deroceras (Aegoceras) planicosta, enlarged sutures after Branco, 
Paleontographica, xxvi, Pl. x. These show the ananepionic suture I, the metane- 
pionic or goniatitic sutures 2-4, and the paranepionic with divided siphonal lobe 
at the diameter of 1 mm. and 2 mm., and the next septum, the 7, here given, is 
transitional to the first neanic septum, the 8 of this series, which shows the begin- 
ning of ammonitic digitations in saddles and lobes and a divided dorsal lobe. 
By comparing this with the sutures of Pl. ii, Fig, 16, Avarcestes lateseptatus, and 
Gephuroceras serratum, Pl. ii, Fig. 17, it will be seen that the ephebic ventral 
lobes and smooth sutures of the Goniatitinze, represented in Gephuroceras, are 
limited to the paranepionic in Deroceras. The goniatitic ventral lobe in other 
words is replaced in the ananeanic of Deroceras, representing the Ammonitinz, 
by the digitate lobes and saddles of that suborder. 
Fig. 3. Vermiceras (Arietites) spiratissimum, enlarged sutures, after Branco, 
(zbid.), Pl. ix, showing also acceleration of development through the replacement 
_of the ephebic characters of the Goniatitinze by those of the Ammonitinz in the 
ananeanic substage. 
Fig. 4-11. Zarphyceras Champlainense, (sp. Whitfield), Hyatt; Loc., Fort 
Cassin; U. S. N. Mus., Walcott Coll. Fig. 4, side view slightly enlarged, show- 
ing involution and small unbilical perforation ; the crack indicates the direction 
of the section given in Fig. 5. Fig. 6 gives general section and the centre is of 
about the same age as Fig. 6. Fig. 7 is younger and shows beginning of the 
dorsal furrow narrower and deeper than in Fig. 6, Fig. 5 shows that it is 
probably due to the mechanical effects of the sudden bending shown in Fig. 7. 
Fig. 8, ideal section showing location of sections Figs. 6 and 7. Fig. 9, section of 
another specimen, natural size, showing a younger stage at the centre. Fig. Io, 
side view of same specimen. Fig. 11, enlarged section of metanepionic centre of 
Fig. 9, showing outline like that of Maztzlus pompilius at the same age. 
Fig. 12-16. Zarphyceras prematurum, Hyatt, Quebec Group; Loc., Port au 
Port, Newfoundland. Fig. 12, side view of fragmentary specimen, natural size, 
giving part of livingchamber. Fig. 13, front view of same. Figs. 14 and 15, front 
and side view of nepionic and part of neanic stage slightly enlarged; Fig. 16, front 
view of nepionic whorl of same (x 2) showing a dorsal furrow and the abrupt 
bending of the whorl. The narrowness of the umbilical shoulders is not natural, 
being probably in part due to the obliquity of the septum and partly to erosion of 
the outline at this point. 
Figs. 17-22. Tarphyceras Aucoini, Hyatt, Quebec Group; Loc., Port au Port, 
Newfoundland. Fig. 17, side view, natural size, of ephebic stage; Fig. 18, part 
of neanic whorl to show sutures. Fig. 19, section of ephebic whorls, natural size, 
of another specimen. Fig. 20, section, natural size, of another specimen, the upper 
whorls a little depressed by pressure; Fig. 21, the nepionic stage enlarged (four 
diameters) to show more accurate outline and the dorsal furrow and sudden bend- 
ing of whorl and narrow umbilical perforation. Fig. 22, side viewofsame. The 
apex in all of these specimens was too much eroded to show the cicatrix. 
*This figure is not numbered. 
