[57] FLOUNDERS AND SOLES. 281 
ANALYSIS OF SPECIES OF ONCOPTERUS. 
a. Body broadly ovate, with regular outlines; mouth small, twisted toward the 
blind side; its teeth small and in bands; maxillary 34 in head; eye 54, twice the 
concave interorbital area; gill-rakers short and slender; left side above eye with 
-a deep horizontal groove, in which lies a depressible curved bone as long as the 
maxillary. This seems to be attached to the first interneural, and is probably a 
modified fin-ray. Onits upper edge on either side is a fringe of short fleshy pro- 
jections resembling the gill fringes, but much shorter. Scales small, mostly smooth. 
Lateral line with a long, low arch, from which four accessory branches extend ver- 
tically upward. Another branch behind curve, and about 6 on head; blind side 
similar; no anal spine. Right ventral of six rays, placed wide apart along the 
ridge of the abdomen, but not joining the anal and not extending forward of the 
isthmus. Left ventral lateral, with narrow base. Color dark brown, everywhere 
covered with whitish stellate spots. Head 32in length. Depth, 2. D., 61. A., 
Vert Gu SCALAS) DLO doc seis al acem eo teiowe Scleelus sts s'scafmia/s~ 2m si DARWINI, 66. 
66. ONCOPTERUS DARWINI. 
Rhombus sp. Darwin, Jenynus, Voyage of the Beagle, Fishes, 1842 (east coast of Pat- 
agonia). 
Oncopterus darwini Steindachner, Ueber Eine neue Gattung, etc, Pleuronectoiden, 1874, 
1 (San Mathias Bay, Eastern Patagonia). 
Habitat.—Eastern coast of Patagonia. 
Of this species we have examined numerous specimens in the Mu- 
seum of Comparative Zoology. Nos.11397 and 11398 are adult examples 
from San Mathias Bay. To this lot belong Dr. Steindachner’s original 
types. . There is also a bottle of young examples (11311, M. C. Z.) from 
Rio Grande do Sul. 
Genus XX VIL.—PLEURONICHTHYS. 
Pleuronichthys Girard, Proc. Ac. Nat. Sci. Phila., 1854, 139 (cawnosus). 
Heteroprosopon Bleeker, Comptes Rendus Acad. Amsterdam, xiii, 1862, 8 (cornutus). 
Parophrys Giinther, Cat. Fishes, iv, 454, 1852 (not of Girard). 
TypPE: Pleuronichthys cenosus Girard. 
This well-marked genus contains three American species, which are 
very closely related to each other. The Asiatic species, Platessa cor- 
nuta Schlegel, of the coasts of China and Japan, is also a member of 
this group, having an accessory branch to the lateral line as in the 
American species. This species bears some resemblance to Pl. verti- 
calis. 
The species of Pleuronichthys are herbivorous. They spawn in the 
spring, and live in comparatively deep water. 
ANALYSIS OF SPECIES OF PLEURONICHTHYS. 
a. Dorsal fin beginning on the level of the lower lip, its first nine rays on the blind 
side; a blunt tubercle at front of upper eye, another at each end of the nar- 
row interorbital ridge, the posterior largest but usually not spine-like ; two 
or three above the latt r, behind the upper eye; some prominences above the 
opercle; head 33; depth 14; D. 72; A. 40; vertebrae 14+26=40; color 
brownish, usually much mottled with brown and gray, often finely speckled 
SMeVOC YANO tinge eateries see alee Soca saad acacais Skaieoe ane DECURRENS, 67, 
