70 
U. S. P. R. R. EXP. AID SURVEYS-ZOOLOGY-GENERAL REPORT. 
guished by the absence also of spines upon the opercle and membranous flaps upon the head ; 
by the lower jaw being overlapped by the upper ; by the existence of an isthmus separating the 
gill openings ; by the presence of five branchiostegals instead of six ; by the separation of the 
dorsal fins ; and, finally, by the fact that there is but one longitudinal band of denticulated 
scales along the dorsal region. 
Its affinities with Scorpcenichthys are much closer than apparent. The membranous flaps 
above the orbits, the continuity of the gill openings under the throat, the presence of spines 
upon the preopercle only, are sufficient proofs of it. Indeed, it can be distinguished from 
Scorpcenichthys simply by the presence of its dorsal band of scales, its five branchiostegals 
instead of six, its anterior dorsal lower than the second, the insertion of the ventrals under the 
pectorals, and which are composed of three soft rays, instead of five. 
The external aspect of Artedius will remind the fresh water bullheads to the most superficial 
observers. The head is large, depressed, and broader than deep, as also the anterior portion of 
the body, whilst posteriorly it is compressed, and very much tapering towards the caudal fin. 
1. ARTEDIUS LATERALIS, Grd. 
Plate XXII a, Figs. 5 & 6. 
Spec. Char. —Surface of head smooth. Preopercle armed with a flat bicuspid spine. Band of dorsal scales narrow, origin¬ 
ating at the thoracic arch and extending to near the terminus of the base of second dorsal. Anterior margin of first dorsal 
situated in advance of the thoracic arch. Deep chestnut brown above, maculated with yellowish ; beneath yellowish. 
Svn. — Scorpaenichthys lateralis, Grd. Proc. Acad. Nat. Sc. Philad. VII, 1854, 145. 
Hemilepidotus nebvlosus, Ayres, MSS. 
Galycilepidolus lateralis, Ayres, Proc. Cal. Acad. Nat. Sc. I, 1855, 77. 
Artedius lateralis, Grd. Proc. Acad. Nat. Sc. Philad. VIII, 1856, 134. 
The head of the specimen before us enters about three times in the length, excluding the 
caudal fin. The occipital region is flattened; the interocular space, which is quite narrow, is 
convex, and the rostral distance declivous. The mouth is broad ; the posterior extremity of the 
maxillary extends to a vertical line drawn posterior to the pupil. The eye is well developed, 
sub-circular in shape, and situated towards the summit of the head ; its horizontal diameter is 
contained a little over four times in the length of the side of the head ; about once in advance of 
the anterior margin of the orbit. The anterior nostril is a little nearer the orbit than the 
extremity of the snout, whilst the posterior is situated posteriorly and inwardly of the latter, in 
a little depression behind a small and acerated spine, terminating the turbinal bones. A 
short and flat bicuspid process may be observed upon the convexity of the preopercle, the 
spines being slightly bent upwards. The rest of the opercular apparatus is perfectly smooth. 
The first dorsal is much longer than high, and its anterior margin is situated anterior to the 
upper part of the insertion of the pectorals, being almost even with a line passing through the 
suprascapular bone ; in advance, therefore, of the posterior and membranous flap of the opercle. 
It is composed of nine slender rays. The second dorsal, which is higher than the first, extends 
from a little distance of the latter to near the insertion of the caudal, the extremities of the posterior 
rays at least reaching almost to the base of that fin. Its rays, seventeen in number, are articu¬ 
lated but undivided. The caudal fin, posteriorly sub-convex, composed of nine bifurcated and 
two simple-rays, with several rudiments. The fin itself is contained about five times and a half in 
the total length. The origin of the anal is situated opposite the fourth ray of the second dorsal, 
and does not extend quite as far posteriorly ; it is composed of eleven slender and undivided rays 
