PLEURONECTID^E. 17 



Genus IV— Zeugopterus, Gottsche. 



Rhombus (part), Lepido rhomb us, and Phrynorhombus, Gunther. 



Branchiostegals seven : pseudobranchim present. Eyes on the left side and close 

 together. Cleft of mouth deep. Sharp villiform teeth in a band in either jaw, 

 present or absent from the vomer. The dorsal fin commences before the upper eye, 

 its rays and those of the anal are nearly all branched. Caudal not united to the 

 vertical fins. The ventrals either free from or united to the anal. Scales ctenoid. 

 Lateral-line having a strong curve anteriorly. 



Steenstrup (Overs. Dansk. Vid. Selsk. 1865, pp. 95-112) pointed out that a 

 large opening exists in the septum which is normally situated between the gills 

 of the two sides : that he observed such in Rhombus megastoma, Donovan : R. 

 cardina, Fries. : R. punctatus, Bloch : and R. unimaculatus, Risso, considering this 

 as indicative that all these forms belong to the same genus, he adopted Gottsche's 

 nomenclature of Zeugopterus. 



Geographical distribution. — Shores of northern Europe, to the south coasts 

 of Great Britain and France. 



The British forms may be subdivided as follows : — 



A. Ventrals not united to the anal. 



1. Zeugopterus unimaculatus, D. 70-80, A. 61-68. Teeth absent from the 

 vomer. 



B. Ventrals united to the anal. 



2. Zeugopterus punctatus, D. 87-101, A. 69-80. Teeth present on the vomer. 



A. Ventrals not united to the anal. 



1. Zeugopterus unimaculatus, Plate XCIX. 



La petite Limandelle, Duhamel, Pesc. iii, sect. 9, p. 270, pi. vi, f. 5. 



Pie uronectes punctatus, Flem. Wern. Mem. ii, p. 241, Phil. Zool. t. iii, f. 2, and 

 Brit. An. p. 196 ; Jenyns, Manual, p. 462 ; Steenstrup, Overs. Dansk. Vid. 

 Selsk. 1865. 



Rhombus punctatus, Yarrell, Brit. Fishes (Ed. 1) ii, p. 247, c. fig. (Ed. 2) ii, 

 p. 338 (Ed. 3) i, p. 650 ; Thompson, Ann. Nat. Hist, ii, p. 271, and Nat. Hist. 

 Ireland, iv, p. 201. 



Rhombus unimaculatus, Risso, Eur. Merid. iii, p. 252, f. 35 ; Nilss. Skan. 

 Fauna, iv, p. 645. 



Rhombus cardina (Cuv.) Kroyer, Dan. Fiske, ii, p. 464. 



Scophthahiius unimaculatus, Bonap. Pesc. Eur. p. 49; Steind. Ich. Span. u. 

 Port. 1868, p. 49. 



Rhombus uniocellatus, Nardo, Prod. Ich. Adriat. no. 135. 



Zeugopterus punctatus, White, Catal. p. 104; Winther, Ich. Dan. Mar. p. 38. 



Phrynorhombus unimaculatus, Gunther, Catal. iv, p. 414; Canestr. Fauna 

 Ital. p. 161 ; Giglioli, Pesc. Ital. p. 38. 



Pletironectes unimaculatus, Moreau, Poiss. France, iii, p. 323. 



Eckstrom's topknot, Couch, Fish. Brit. Isles, iii, p. 175, pi. clxvii. 



B. vii, D. 70-80, P. 10-12, V. 6, A. 61-68, C. 16. 



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