132 Part ITI.—Twenty-fourth Annual Report 
examined in side view the ethmoid in esmarkii (Z., fig. 9, pl. xi.) is 
seen to slope backwards quickly, whereas in minutus (fig. 6, ib.) and 
luscus (fig. 3, 2b.) it is more nearly vertical. 
There are few distinguishing features between the skulls of Juseus and 
minutus, even when they are compared side by side. To convert these 
differences into characters by which the skull might be recognised apart 
from the other is well nigh impossible, so closely are they related. 
A general contrast will, therefore, be made between the two. 
In two fish of the same size the skull of ménutus was the larger—it 
was slightly longer and higher. 
Seen from above, when the skull is resting on the vomer and the par- 
asphenoid, the calcified base of the ethmoid (E.) is partly hidden by the 
crest of the bone in duscus (fig. 4); in ménutus the whole of the base is 
visible (fig. 8). 
The processes from the parietals (P. pr.) are large, winglike, in luscus ; 
they are narrow in minutus. The squamosals (Sq.) project posteriorly 
farther in Zuscws than in minutus. The notch between the frontal (F.) 
and post-frontal (pt.-F.) which receives the mucous canal passing 
round the eye, is much smaller in minutus than in luscus. The frontal 
in /wscus contracts a little over the orbits and then expands again into a 
broadened anterior extremity. In minutus it comes to its narrowest over 
the orbits, and is continued forward with the same breadth. 
The breadth of the anterior end of the skull, measured from the outer 
angle of one pre-frontal (pr.-F.) to the outer angle of the other, is in luseus 
greater than in minutus. 
Side view.—The occipital spine (Oc. Sp.) of duscus (fig. 3) is much 
higher than that of minutus (fig. 6). The part of the spine on the 
frontal rises more rapidly in the former. 
The hind edge of the occipital spine may be straight, or it may be 
slightly incurved just before reaching the occipital foramen. 
The front edge of the ethmoid has less backward slope in /uscus than 
in minutus. 
In minutus the pre-frontal rises up to meet the outer corner of the 
frontal: it raises the latter a little. In duscws it does not rise so much. 
Seen from below, the pre-frontal is roughly of a quadrant shape in 
luscus (fig. 12), and of a sextant shape in minutus (fig. 11). 
The parasphenoid (P.s) is more slender in minutus than in luscus. 
The brain-case is more spherical in shape in minutus than in luscus. 
Seen from behind, the squamosal (Sq.) bends outwards and upwards 
in luscus (fig. 5). In minutus it projects more in a horizontal direction 
fie at) 
ithe opisthotic (op. O.) forms in minutus a projecting angle where the 
post-temporal articulates with it; this angle was not noticed in luscus. 
The par-occipital (par.-Oc.) of /wscus is continued backwards in a pro- 
jecting angle (Ang.), and in consequence the edge of the ex-occipital 
(e.-Oc., fig. 3) curves downward in a concave sense to the articulation 
with the shorter arm of the post-temporal. It is thus contrasted strongly 
with the blunt termination of the par-occipital in minutus (fig. 6). 
The skull of esmarkit is long when compared with that of minutus. 
An esmarkit measuring 15*dcm. in length had a skull equal in length to 
that of a minutus 21cm. long. 
The ethmoid slopes back very quickly in esmarkw (fig. 9). The 
frontal is narrow over the eyes, and the pre-frontals stand out prominently 
laterally, but the breadth across them is small (fig. 10). 
The yomer projects further in front of the pre-frontals-in esmarki 
fig. 13) than in minutus and Juscus. 
