416 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 
contained 2.82 to 3.05 times in the spine (only 2.0 times in the 
largest specimen). The third ray of the first dorsal is contained 
from 1.05 to 1.25 times in the head. The base of the first dorsal 
fin contains the length of the snout from 1.0 to 1.2 times, and itself 
is contained from 1.0 to 1.25 times in the interval between the end 
of the first dorsal and the first of the small anterior rays of the 
second dorsal. The length of the pectoral fin is contained 1.5 
times in the head; it is not produced, but somewhat pointed, the 
fifth ray being longest. The filamentous outer ventral ray, reach- 
ing at most to the fifth anal ray, is contained 1.35 to 1.6 times in 
the head; its insertion is slightly behind the vertical from the origin 
of the first dorsal. 
The ground color in alcohol is light yellowish brown, becoming 
duller on the belly and head, darker on the snout and opercle. The 
margins of the mouth, the edges of the nostrils, the eye, and the 
branchiostegal membranes opposite the opercle, are blackish. The 
sides of the head and the belly are underlain with silvery. The fins 
are blackish, becoming lighter basally. The lining of the buccal 
and branchial cavities is blackish; the parietal peritoneum is 
brownish. 
C. tydemani differs from the other species of the same group 
(as defined after the description of the last species) as follows: 
from (. marginatus, in the smaller eye, darker color, and arrange- 
ment of spinules on the scales; from C. microps, in the larger eye, 
more numerous ventral rays, darker color, and in the arrangement 
of the spinules oj the scales; and from specimens of C. macrolophus 
(Alcock)? of similar size, in the much longer dorsal spine, with 
fewer serrations, and in the smaller scales; both Alcock and Brauer 
counted 5 or 6 scales from the end of the first dorsal to the lateral 
line, including the lateral line scale; while C. tydemani has 7, ex- 
clusive of the lateral line scale. C’. tydemani is closely related also to 
0. semiscaber, from which species it differs as follows: 
Snout longer than orbit, instead of being equal to it, and contained 3.4 
to 3.5 instead of 3.7 times in the length of the head. 
2. Orbit shorter, 4.0 to 4.2 (to 5; Weber) instead of 3.7. 
3. Spinules on scales less regularly arranged in parallel series, it being 
possible to align them in quincunx order. 
4. The rostral tubercles smaller; the spinules on the terminal tubercle 
weaker and not arranged in definite radiating series. 
5. The distance is greater between the anus and the base of the ventrals, and 
shorter between the base of the ventrals and the isthmus. 
6. The second dorsal spine is stronger and very much longer, and is armed 
with fewer serrations, which are confined much more closely to the basal portion 
of the spine. 
1 See note on O. macrolophus, after the description of this species. 
