10 
U. S. P. R R. EXP. AND SURVEYS-ZOOLOGY-GENERAL REPORT. 
2. AMBLOPLITES INTERRUPTS, Grd. 
The Perch of the San Franciscans. 
Plate II, Figs. 1—4. 
Spec. Char. —Posterior extremity of maxillary reaching a vertical line drawn back of the pupil. Posterior margin of caudal 
fin sub-emarginated. Origin of anal fin opposite the eleventh ray of the dorsal. Interrupted dark bands on the sides. Two 
streaks diverging from the eye—one running towards the opercular spot, the other obliquely downwards. 
Syn. — Centrarchus interruptus, Grd. Proc. Acad. Nat. Sc. Philad. VII, 1854, 129, and VIII, 1856, 132. 
Cenlrarchus maculosus, Ayres, Proc. Cal. Acad. Nat Sc. I, 1854, 8 ; & in Proc. Bost. Soc. Nat. Hist. V, 1855, 99. 
Perch in San Francisco. 
The general form is rather elongated, and very much compressed. The nuchal region is 
convex, whilst the oculo-cephalic is depressed or sub-concave. The head forms a little less than 
the third of the total length. The snout is tapering, and the lower jaw the longest.. The 
mouth is rather large ; its cleft oblique upwards. The posterior extremity of the maxillary, 
which is considerably dilated, reaches a vertical line drawn back of the pupil. The eye is large 
and circular, comprised about four times, or a little more, in the length of the side of the head. 
The opercular apparatus has neither spines nor serratures. The gill openings are continuous 
under the head, and there are six branchial rays. The origin of the dorsal nearly corresponds 
with a line passing along the margin of the opercular flap ; it is composed of thirteen spiny 
rays and eight to eleven soft and articulated ones. The base of the spinous portion is twice the 
length of the soft; the latter is higher than any of the spines. The first, or anterior spine, is 
exceedingly small, the second is twice as high ; the others increase till the sixth, seventh, and 
eighth, when they again diminish to the twelfth ; the thirteenth is a little higher than the few 
preceding ones. The lobes of the caudal are rounded; the middle of the posterior margin is 
slightly concave. The fin itself constitutes nearly the sixth of the entire length. The origin 
of the anal is placed opposite the eleventh dorsal spine ; it is composed of six or seven spines, 
and nine or ten articulated rays ; the space occupied by the spines is equal in length to that 
over which the soft rays are inserted. The vent is situated somewhat in advance of the anal 
fin. The origin of the ventrals corresponds to the vertical line passing in front of the base of 
the pectorals; their spine is long and acute, and the tips of the soft rays overlap the vent. The 
tips of the pectorals extend a little further backwards than that of the ventrals ; the origin of 
both the ventrals and pectorals, is a little in advance of the origin of the dorsal. 
Br. VI—VI. D XIII, 8—11 ; A VI or VII, 9 or 10 ; C 5, 1, 8, 7, 1, 4; V I, 5 ; P 13. 
The scales are of moderate development, higher than long, provided upon their posterior 
margin with several series of minute spines. The lateral line is concurrent with the dorsal 
outline. The scales on the cheeks are a little smaller than on the opercular apparatus, either 
of which being almost entirely smooth upon their posterior margin. The upper surface of the 
head and jaw are smooth and naked. 
Ground color greyish brown above, silvery grey beneath. Irregular transverse bands of dark 
brown or black, interrupted along the lateral line, the portion of the band above it being some¬ 
what alternating with the portion beneath it. A large black spot may be observed at the upper 
and posterior angle of the opercle. Two vittee or streaks diverge from the eye backwards. 
References to the figures. —Plate II, fig. 1, represents Ambloplites interruptus in profile and size 
of life. Fig. 2 is a scale from the dorsal region. Fig. 3, a scale from the lateral line. Fig. 4, 
a scale from the abdominal region. 
