PALAZFONTOGENY AND PHYLOGENY 521 
This way lies the truth, and not in groundless speculations 
such as many students of cephalopods are prone to indulge in. 
Method of working.—In order to succeed, one must select 
material with great care, preferably limestone that is soft but 
not so weathered as to crumble, nor so brittle as to shatter. 
One’s finger nail and some steel dental chisels are all the tools 
needed for breaking off the outer whorls of young ammonites. A 
microscope with thirty diameters magnifying power is the most 
satisfactory, although higher powers are occasionally needed. 
For studying surface markings a strong pocket lens is usually 
sufficient; the specimen should then be placed dry on white 
cardboard. For observing the sutures, or shape of the whorls, 
the specimen should be placed on cardboard in a drop of water, 
spread out so as not to distort the object. The water, being 
slightly viscous, will also hold the small object in any position. 
For taking measurements a micrometer eyepiece is needed, 
especially in drawing, for the camera lucida is not very satisfactory 
for drawing opaque objects. Sections can easily be cut by 
grinding with emery powder on a glass plate. 
The accompanying illustrations will give an idea of how the 
facts are ascertained. A number of well-preserved adults of a 
species are selected, and the outer coils are pulled off piece at a 
time under water, until a complete series is obtained, represent- 
ing every change .in growth. All the pieces of whorls are pre- 
served, but often it is possible to have a complete series in one 
specimen. The individuals representing stages of growth are 
kept separate, in small glass tubes attached to cards for labels, 
on which are noted the measurements of the specimen, stage of 
growth, and such other facts as are wanted for ready reference. 
On plate A are shown the results of some work of this char- 
acter. The species selected was Schloenbachia aff. chicoensts 
Trask, from the upper Horsetown beds, top of Lower Creta- 
ceous, from Phcenix, Oregon. Fig. 1 shows the protoconch with 
part of the first whorl drawn as if unrolled. The protoconch is 
phylembryonic, representing the primitive ammonoid; the first 
suture, angustisellate, with narrow lateral lobes and saddles, is 
