32 ZOOLOGY. 
PERCILIA GILLISSII, Girard. 
Pirate XXIX, Figs. 5—9. 
Spec, cHAR. Snout short and rounded ; mouth small; posterior extremity of upper maxillary 
corresponding to the vertical of the anterior rim of the eye. A few minute spines upon the 
angle of preopercle. Scales large, conspicuously ciliated posteriorly. Ground-color light red- 
dish, or reddish brown, maculated with black. 
Syn. Percilia Gillissii, Grp. Proc. Acad. Nat. Se. Philad. VII, 1854, 197. 
Descr. This is a comparatively small species, and in all probability the specimens before us 
are full-grown ones. The largest we have seen measure about three inches and a half in total 
length, of which the head constitutes the fourth part. The dorsal and abdominal outlines are 
convex, giving to the whole profile a fusiform aspect. The peduncle of the tail is moderately 
developed, and rather narrow. The greatest depth, measured in advance of the first dorsal, is 
contained three times in the length, the caudal fin excluded; the least depth, taken on the 
peduncle of: the tail, enters seven times in the same dimension. The greatest thickness equals 
half the greatest depth. The body, therefore, is much compressed. The occipital region is 
slightly depressed. The snout is short and rounded, and the upper jaw, which is slightly pro- 
tractile, overlaps a little the lower one. The mouth is quite small, the posterior extremity of 
the upper maxillary extending to a vertical line, which would pass immediately in advance of 
the anterior rim of the orbit. The maxillary teeth are small, subcylindrical, slightly tapering 
towards their point, and disposed upon several rows. The front of the vomer is provided with | 
a subtransverse narrow band of card-like teeth, and not very conspicuous. The palatine bones 
are smooth. The pharyngobranchials are well developed, and densely covered with minute 
prickles. The tongue is smooth, small, semi-elliptical in shape, and very much -flattened, 
mayhap more swollen in a living state. The eye is of medium size, and subcircular ; its hori- 
zontal diameter being contained nearly four times anda half in the length of the side of the 
head. The preopercle exhibits but a few minute spines upon its limb; the opercle has no 
spine at all ; and the inferior edge of both the sub and interopercle is entire, or else not cre- 
nated. The gill openings are continuous under the throat, but there is a membranous expan- 
sion between the adjoining branchiostegals, thus filling up a space which is open in the species 
of Percichthys, above described. The branchiostegals are five or six in number, flattened, and 
recurved. The suprascapular is not visible externally ; the coracoid expands much less above 
the base of pectorals than in Percichthys ; and, moreover, these bones are neither provided 
with spines nor crenated upon their edges. 
The dorsal fins are similar in general appearance to those of the foregoing percoids; the 
membrane which unites the spines is deeply emarginated ; but the two intermediate spines be- 
tween these two fins do not exist in this species. There are, consequently, nine dorsal spiny 
rays. The ninth, which is closely connected with the posterior fin, is the smallest of all; the 
eighth comes next, and is but very little higher than the latter ; the others increase in height, 
as follows: first, seventh, sixth, second, fifth, third, and fourth. There are instances where 
the third is slightly higher than the fourth, as is also the case in Percichthys chilensis. The 
second dorsal is not quite as high as the first, though a little higher than its own base ; on the 
other hand, the base of the first dorsal is longer than its height. The middle rays bifurcate 
twice upon their length, and their tips extend a little further backwards than those of the anal. 
The latter is preceded by three spines similar to those in Percichthys chilensis and allied species. 
A few of the central soft rays exhibit traces of a bifurcation of the third order; the others 
are as in the second dorsal, the external margin of which fin is rounded or subconvex, as is 
the case in the anal. The caudal is broad and subcrescentic upon its posterior edge, the cen- 
tral rays bifurcating three times. The insertion of ventrals is situated behind the base of the 
