Larval Stages of Trilohites. — Beecher. 171 
The second stage (figure 4) is decidedly more elongate ; the 
axis is more distinctly annulated ; the occipital pleura defined % 
and the pygidium is larger and has an additional segment. 
Ptyclioparia kinyi Meek; plate VIII, figures 5,6 and 7; 
from the Cambrian of Nevada and Utah. Figure 5 represents 
a cast of the protaspis, and shows a defined occipital ring, 
with the axis slightly expanded and undefined in front ; py- 
gidium truncate behind. Figure 6, which is referred to a 
later stage (metaprotaspis) of the same species, shows the in- 
ception of several characters that have not as yet appeared in 
the previous larva;. The axis is very strongly annulated ; the 
anterior lobe is nearly as long as the four posterior annula- 
tions of the cephalon, and on each side there is a furrow rep- 
resenting the eye-line of the adult ; the free-cheeks are pres- 
ent as narrow marginal plates, including the genal spines; the 
pygidium shows two segments separated by a fvirrow. 
An adult Pfychoparia kliujl is shown in figure 7 and may 
be taken as representing the sum of the changes passed 
through in the development of larvie like the preceding, be- 
longing to the genera iSoIe)iopIei(ra, Llosfracus and Pfycho- 
paria. The introduction and growth of the segments of the 
thorax are perhaps the most marked changes, but other points 
of importance to be noted are : the comparatively smaller size 
of the cephalon and its transverse form; the limitation and 
recession of the glabella, which is now rounded in front, and 
only extends about two-thirds the length of the cephalon ; the 
growth of the eyes and free-cheeks at the expense of the fixed- 
cheeks; the increased segmentation of the abdomen, shown in 
the axial and pleural grooves on the pygidium. 
Sao /lirstifa Barrande ; plate VIII, figures 8, 9, 10 and 11 ; from 
the Cambrian of Bohemia; after Barrande.-' The specimens of 
this species are preserved as casts, and several of the features 
are therefore somewhat sul)dued. The earliest or anaprotaspis 
stage, represented in figure S, is (juite as primitive in most re- 
spects as any of the preceding. It is circular in outline, the 
annulations of the axis are distinctly sliown only in the neck 
segment and pygidial portion, and the eye-line is present. In 
figure 9 of the metaprotaspis, (juite an advance is seen in the 
development of the free-cheeks and the more pronounced an- 
nulation of the glabella, together with pleural grooves from 
