Tim Scope of Paleo)itolog>j. — W(Uiairu<. 159 
Every geologist is familiar Avith the more apparent features of 
the series as seen in the genera Nautilus, Goniatitfx, Ccratitcs 
and Ammonites. 
The various degrees and forms of lobes and saddles are the 
basis of elaborate classifications and S3^stems of names proposed 
by Beyrich, the Sandbergers and others, but up to the present 
time 1 think we have not a published classification which recog- 
nizes the fundamental law of evolution expressed in the series. 
In analyzing the forms of suture, for my class in the History 
of Organisms, I found the following simple law to exist. 
The various suture lines of the chambered cephalopod shells 
can be distinguished by the differences in degree of complexity 
of the crimping of the edge of the septum. 
Viz: (aj In the Ortli<iceran and Ndvti/ian type, the edge of the 
septum is straight, or the curving is not enough to produce more 
than a single oscillation of the suture line during its complete 
circumference. 
(b) The Goniatite septum presents a lobed suture, but the edges 
of ail the lobes and saddles are simple. 
(c) In the third type the lobes and saddles are variously crenu- 
lated. In the C<ratite the crenulation aft'ects the base of the 
lobes, in IL-lictitcs the top of the saddles is crenulated, and in 
MendJicottia the lobes, the saddles and the connecting parts of 
the suture are crenulated. 
(d) In the typical Aininojiitc there is a tertiary crimping of 
the suture line, ('. c , each of the archings of the line correspond- 
ing to the crenulations of Mendlicottia is again crenulated, form- 
ing a complexl}- foliate suture. 
(e) In the adult forms of Piudcoceras there is a still further 
elaboration of the crimping, the tertiary archings of the Ammon- 
ite are again crenulated, forming a quaternary stage of corruga- 
tion. 
The series presents a gradual elaboration of the crimping of 
the edge of the septum, forming a suture line, 1st, simple, 2d, 
primarily lobrd. Hd, secondarily corrugated or the crcniilatcd 
type, 4th, tertiarily corrugated or the foliate type, and 5th, the 
qu.atirnary cor rncfaf ions of Pinacoceras. 
In their historical bearings it may V)e said of this series that, 
1st. It is the order in which the various types make their first 
appearance in the geological series. 
