1886.] An Interesting Connecting Genus of Chordata. 1029 
by the plate of Bothriolepis, but differing from it in being contin- 
uous anteriorly and posteriorly with the rest of the buckler. 
This structure makes it probable that the median orifice of the 
Pterichthyidz represents both protostome (nares) and orbits, and 
that these orifices have become differentiated in later forms. The 
protostome in Bothriolepis is covered by a probably movable 
valve. That the organ of smell should have been differentiated 
from a primitive mouth is altogether reasonable in view of the 
close relationship subsisting between these senses; but that the 
sense of sight should have had acommon orifice is not to be antici- 
pated. The recent re- 
markable discovery of a 
_Tudimental eye in the pi- 
heal gland of lizards does — 
not throw much light on 
the subject, since true 
eyes coexist with it in 
those animals, and the 
median eyes of the Pter- 
ichthyidæ had left the 
_ field long before the ad- 
He ` vent of Reptilia, in a phy- 
~ logenetic sense. From a 
. chronological point of 
_ View it is not unlikely 
_ that the present new ge- 
: = brings such forms Fic. 1.—Mycterops ordinatus Cope. Cranial 
closer. together, since and cocks buckler from above, 3% natural size. 
there is little doubt but that the Pelycosauria of the Permian 
Possessed large pineal eyes. 
= The new genus here referred to may be named Mycterops, and 
the > Single species which thus far represents it may be called Myc- 
ollows : 
acute spine-like 
directed back- 
‘suture from the cranial buckler. 
The species characters are as foll 
aoa “dite rounded. Cas . 
