ORDER II OPISTHOPARIA 627 
rudimentary or absent. Thorax with from fourteen to seventeen segments. Pygidium 
small and of few segments. Cambrian. 
The genera comprised under this family present a number of very primitive 
characters, such as are displayed only in the larval stages of higher forms. The free 
cheeks are narrow and marginal, and may 
be compared with those in the nepionic 
stages of Sao and Ptychoparia. Eyes have 
not been detected, but the presence of an 
eye-line suggests their possible existence. 
The variations in the glabella are very 
marked, and are as great as those which in 
higher forms attain some importance as 
family characteristics. 
So far as known, all the larval forms 
in the other families of the Opisthoparia 
agree in haying the narrow marginal free 
cheeks, bearing the genal angles. The eye- 
line is present in most of the adult Olenidae, 

Fic. 1290. 
Cephalon of Cono- 
coryphe Sulzeri, 
Schloth. 

and in the early stages of all so far as = 
known, so that the general average of char- Fic. 1289. 
acters in the Conocoryphidae represents the — Conocoryphe Sulzeri, Schloth. Fic. 1291. 
main larval features throughout the other Without the freecheeks. Cam- ~  Cephalonof Atops 
aN F 5 brian (Et. C); Ginetz, trilineatus, Em- 
families. Bohemia. 1/}. mons. 
Conocoryphe, Corda — (Conocephalites, 
Barr.), (Figs. 1289, 1290). Cephalon semicircular ; genal angles produced into spines ; 
glabella distinctly lobed, wide behind and contracted in front, not extending to the 
frontal border. Fixed cheeks very large, with conspicuous furrow parallel to the 
anterior margin; free cheeks narrow, marginal; thorax of fourteen segments. Cam- 
brian ; Europe and North America. 
Atops, Emmons (Fig. 1291). Differs from Conocoryphe in having a more cylin- 
drical and longer glabella, small pygidium, and seventeen free segments. Lower 
Cambrian ; North America. 
Ctenocephalus, Corda. Like Conocoryphe, but with a lobe in front of the glabella, 
which is also less strongly defined ; free cheeks larger ; pygidium much smaller; free 
segments fifteen. Cambrian; Europe and North America. 
Bathynotus, Hall. Differs fron. Atops and Conocoryphe in its wider axis; free 
cheeks united in front and extending backward into long genal spines; thoracic seg- 
ments thirteen ; pleura hastate. Lower Cambrian ; North America. 
Family 2. Olenidae. Salter. 
Cephalon larger than the pygidium, usually wider than long ; genal angles commonly 
produced into spines; free cheeks separate. Facial suture extending forward from the 
posterior margin of cephalon along the eye-lobes, and either cutting the anterior margin 
separately, or meeting on the median line. Eyes crescentic, reniform, or semicircular, 
situated at the ends of eye-lines in all but the highest genera. Trunk long, composed of 
from eight (2) to twenty-six free segments. Pygidiwm frequently small; margin entire or 
spinose. Prineipally Cambrian, but extending also into the Ordovician. 
Paradozides, Brongt. (Figs. 1292, 1293). Glabella enlarging in front, lobes 
defined ; thorax with from seventeen to twenty free segments, pleura with spiniform 
or hastate extremities; pygidium a small plate-like termination of the axis, seg- 
mented. Individuals sometimes attaining a length of 0°6 m. or more, Very abundant 
in the Middle Cambrian of Europe, North America, and Australia. 
