170 The American Geologist. September, 1895 
(2) Some of the sediments carefully examined by the writer 
could preserve smaller larval trilobites were such originally 
present and provided with a chitinous test, as shown by the 
abundance of minute ostracodes, and the perfection of detail 
in these and other fossils. 
(3) The protasi)is can be shown to be structurally closely 
related to the nauplius, and in a more marked degree possesses 
some characters required in the theoretical crustacean an- 
cestor. 
III. Review of Larval Stages of Trilobites. 
Matthew-'^' -^ has carefully described several early larval 
(protaspis) stages of trilobites from the Cambrian rocks of 
New Brunswick, which are very simple and primitive, and will 
be noticed first. 
SoIenopJeHi'd rohhi Hartt; plate VIII, figure 1; from the 
Cambrian of New Brunswick ; after Matthew.-^ This larva is 
very minute and circular in outline ; the glabella is obscurely 
annulated and extends to the anterior margin, where it is ex- 
panded ; the neck ring is the only one well defined ; the ab- 
dominal portion is less than one-third the whole length, and 
is limited by a slight transverse furrow; no traces of eyes or 
free-cheeks discernible. 
Liostrcicus onatKjoiidianKs Hartt; ])late VIII, figure 2; from 
the Cambrian of New Brunswick ; after Matthew.-^ This 
form is similar to the preceding, though larger, and with the 
glabella more rapidly expanding in front. The neck segment 
is the only one which is distinct. 
It should be mentioned that most of the larval specimens 
here descx'ibed and figured are preserved in fine shales and 
slates, as cagts of the interior of the dorsal shield, so that 
some features are not as emphatic as on the exterior of the 
test. When well preserved, the axis always shows the typical 
five annulations on the cephalon. 
Pfi/chop(iria l/itnarsso/ti Walcott ; plate VIII, figures 3 and 
4; from the Cambrian of New Brunswick; after Matthew.^* 
The earliest stage is slightly more elongate than the preced- 
ing forms. The axis is narrow, expanding in front and ob- 
scurely annulated, five annulations belonging to the cephalon, 
and one to the pygidiuni, which is very short and separated 
from the cephalon by a distinct groove. 
