[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 3£ in head; eye 5^, 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. On its 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 3f in lengtli. Depth, 2. D., 61. A., 

 45. V., (5. Scales, 115 Darwini, (JG. 



66. ONCOPTSRUS DARWINI. 



Rhombus sp. Darwin, Jenyns, Voyage of the Beagle, Fishes, 1842 (east coast of Pat- 

 agonia). 



Oncopterus darwini Steindachuer, Ueber Eine neueGattung, 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. Xos. 11397 and 1139S are a dult examples 

 from Sau Mathias Bay. To this lot beloug Dr. Steindachner's. original 

 types. There is also a bottle of young examples (11311, M. C. Z.) from 

 Rio Grande do Sul. 



Genus XXVI.— PLEURONICHTHYS. 



Pleuronichthys Girard, Proc. Ac. Nat. Sci. Phila., 1854, 139 (coenosus). 

 Heteroprosopon Bleeker, Coinptes Rendus Acad. Amsterdam, xiii, 1862, 8 (cornulus). 

 Parophrys Giinther, Cat. Fishes, iv, 454, 1852 (not of Girard). 



Type : Pleuronichthys coenosus Girard. 



This well-marked geuns contains three Araericau 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 au accessory branch to the lateral line as in the 

 American species. This species bears some resemblance to PL verti- 

 califr 



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 tbe 

 opercle; head 3£; depth If; D. 72; A. 40; vertebrae 14+26 = 40; color 

 brownish, usually much mottled with brown and gray, often finely speckled 

 on body and fins ...Decurrens, 67. 



