PALAZONTOGENY AND PHYLOGENY 523 
ananepionic; the second suture with the abdominal lobe is meta- 
nepionic, and represents the ammonoid radicle Anarcestes; the 
third and fourth sutures correspond to Jornoceras and Prionoceras ; 
the fifth suture is*a transition from Prionoceras to Glyphioceras ; 
and the sixth with the divided ventral lobe represents Glyphuoceras. 
Fig. 2 shows the larval stage, at diameter of 0™”.68, three- 
fourths of the first whorl. It has a low broad involute whorl, 
with divided ventral lobe, one lateral lobe, and another on the 
umbilical border. This stage is paranepionic, and is like the 
older species of Glyphioceras. 
Fig. 3 shows the development of the sutures from the third 
to the tenth, on a specimen of diameter 0™™.64. 
Fig. 4 shows the advanced Glyphioceras stage, with lobes and 
saddles, well developed, at diameter of 1™™.20; the second lat- 
eral lobe already begins to show on the umbilical shoulder. 
This stage is transitional to Gastrioceras. 
Fig. 5 shows the end of the paranepionic stage, correspond- 
ing to Paralegoceras, at 2™.25 diameter; the umbilicus widens, 
the whorls become higher and narrower, and a third lateral lobe 
appears on the umbilical border. The sutures still remain goni- 
atitic, but in the next stage, ananeanic, ammonitic ornamenta- 
tion, in the shape of a keel, appears at 2™™.70; and at 3™™.20 
diameter the first lateral saddle becomes indented, and the 
adolescent stage is well along. 
Fig. 6 shows a cross section through the center, diameter 
6™™".25, four whorls, paraneanic. The inner whorls are low and 
broad, and the later ones become successively higher and _ nar- 
rower in proportion. 
Fig. 7 shows a section through the protoconch, diameter 
22™™ 2c, six whorls, adult stage; the relative increase of height 
of the whorls and the squaring of the abdominal shoulder is’ 
quite marked as the adult stage advances. 
On these figures may be seen increase in number of lobes and 
saddles, change in position of the siphon from median to exter- 
nal, and the development of the whorls, in height, width, and 
involution. 
