116 THE ROYAL SOCIETY OF CANADA 
the glabella. The three species of Basilicus described by Schmidt from 
Russia are not the Basilicus of Salter, but belong to this genus Ogygites. 
In addition to the difference in the course of the suture, the pygidium 
in this genus is less strongly ribbed. Ogygites is a close parallel to 
Ogygia corndensis, the two forms being almost exactly alike in general 
appearance, in the course of the facial suture, the number of ribs, form 
of glabella, and otherwise, but Ogygia corndensis, to which I have ap- 
plied the generic name Ogyginus, has an entire hypostoma. 
The next step in the development from Basilicus and Ogygites is 
seen in the genus Pseudasaphus Schmidt, in which the course of the 
anterior portions of the facial suture is still further within the mar- 
gin, the glabellar furrows are less prominent, the pygidium shows fewer 
traces of segmentation, and the doublure of the pygidium becomes very 
wide. The culmination of this line of development is seen in Ptychopyge, 
Angelin, where the eyes are very close to the glabella, the facial sutures 
far within the border, the glabella short and faintly furrowed, the 
pleural lobes of the pygidium smooth, and the doublure of the pygidium 
so broad that it underlies all parts of the pygidium except the axial lobe. 
Development in the other Group. 
The oldest of the Asaphids is Ogygopsis, a representative of the 
group with entire hypostomas. This genus has even more primitive 
characters than Basilicus, for, in addition to the strongly ribbed pygi- 
dium, the long glabella, and the marginal facial suture, it has the eyes 
very distant from the glabella, and retains the eye-lines. 
A direct descendant of Ogygopsis is Ogygiocaris, Angelin, of the 
Tremadoc and Llandeilo. This name must be applied to those species 
which are usually looked upon as typical Ogygias, namely Ogygia buchit 
and O. dilatata, for it seems that the types to which Brongniart origin- 
ally applied the name have turned out to be trilobites with forked 
hypostomas, and the Ogygias of England and Scandinavia can not be 
placed in the same genus with them. 
The development in the line from Ogygopsis is parallel to that seen 
in the species with the forked hypostomas, the result being the elimina- 
tion of furrows from the dorsal surface of the crust. Unfortunately, 
however, there seem to be many gaps in the line of development, and 
we have mostly the terminal and widely separated results of the process, 
with few of the connecting links. 
There seem to be three lines diverging from the Ogygopsis stock; 
one in which the glabella remains long and the head short and wide, 
leading to Nileus. In a second, the cephalon becomes elongate, the 
