236 EDWARD PHELPS ALLIS, JR. 
of the myodome, breaks down, but its median portion still 
persists as part of the floor of the cavum cerebrale cranii, and, 
anterior to the hypophysis, it is perforated by the internal 
earotids in their passage from the myodome into the cavum 
cerebrale cranu. 
Thus the prootic bridge of this small specimen of Cottus 
scorplus is nowhere formed by cartilage, and if it be of carti- 
lage in the adult, it must be a later chondrification of the mem- 
brane that, in this specimen, forms the floor of the cavum cere- 
brale cranil. That this does take place is probable, for a car- 
tilaginous prootic bridge is developed relatively late in other 
fishes also, as will be explained later. 
In a 37-mm. specimen of Clinocottus analis the conditions 
resemble those in Cottus scorpeus, differing only in that the 
horizontal myodomic membrane takes no direct part in the 
formation of the floor of the cavum cerebrale cranii, simply 
arching upward to such an extent that it is in contact with, and 
partly fused with, the membranous prootic bridge, thus sep- 
arating the myodome into median and lateral, instead of dorsal 
and ventral compartments (fig. 19). 
The internal carotid arteries of Cottus and Clinocottus are 
strictly similar in their course and branches to those of Trigla. 
The cross-commissure of the efferent pseudobranchial arteries 
has a position strictly similar to that of the latter fish, and the 
nervus palatinus facialis of Cottus is as in Scorpaena, while 
that of Clinocottus is as in Trigla. An anterior portion of the 
ascending process of the parasphenoid has the position of, and 
replaces, the alisphenoid of Amia. 
In none of these small specimens of the Loricati is either the 
dorsal or the ventral compartment of the myodome definitely 
closed toward the orbit by membrane, as, in my earlier work on 
these fishes, I said was the case in the adults. Both in embryos 
and the adult the spinal portion of each compartment opens 
into the prespinal portion, and in embryos this latter portion 
is largely open toward the orbit. In the adult the myodome 
is doubtless closed toward the orbits by connective tissues which 
develop around the rectus muscles as they enter it. In the 
