MUSEUM OF COMPARATIVE ZOOLOGY. 9 
a postparietal or epiotic process ; this process, with a pore (/) in front 
of it, recalls a similar arrangement on the skull of Rhina. The third ((), 
pterotic, is formed by the backward extension of the edge of the cup 
receiving the end of the hyomandibular. This process is quite promi- 
nent ; its height is more than half that of the skull, and the upper angle 
is produced. The articular depression, extended by this process, meas- 
ures about five eighths of an inch in length by one fourth of an inch in 
height. The articulation permits the hyomandibular to lie against the 
side of the skull, or to be turned sidewise at an angle of forty-five de- 
grees. On the side of the skull appear the openings for the second to 
the seventh pairs of nerves (2 to 7), the nostrils (c), and the orbito-nasal 
canal (w). In the orbit the articular facet for the palatal or trabecular 
process of the quadrato-pterygoid (tp) extends nearly to the top of the 
skull, and is produced below the floor in a prominent ridge. Immedi- 
ately in front of the deep cavity in which is found the opening for the 
fifth pair of nerves (5) is the short style (os) connecting with the eye- 
ball. In the section (Plate VII.) the opening for the optic nerve (2) is 
shown to be farther forward and upward than in the Notidanide ; the 
olfactory lobe passes out but a short distance in front of it. Between 
and below the openings for the fourth and fifth pairs there are carti- 
laginous bridges (w, 7). The pituitary cavity (py) is shallow, and 
around the opening for the internal carotid the wall is thin. The 
thread-like termination of the notochord lies close to the lower face 
of the wall. Around it, in the parachordal region, the cartilage is hard 
or granular. 
There are no spiracular cartilages (metapterygoids). 
The Jaws and Hyoid Cartilages. 
Plates VII.-IX. 
Labial cartilages at the angles of the mouth and along the jaws have 
not been found. 
The suspensorium, hyomandibular (hm), is about three inches long, 
depressed, curved, and tapers in the hinder third of its length, where 
applied to the pterygo-quadrate. Its thickness is about one half of its 
width. The curvature is but moderate, certainly not more than that 
of a circle with a diameter of six inches. The end articulating with 
the ceratohyal is small. Anteriorly the articulating surface is oblique, 
forming an angle of about forty-five degrees with the shaft ; posteriorly 
the shaft has tapered to less than half its width. The inner (hinder) 
edge is sharper, and bears nine branchial rays (br-r). 
