142 OPHIDIA. 



Fig. 5, exhibits the shape arid the number of dorsal rows of scales. 

 Fig. 6, represents the vent and the surrounding scutellae. 



GENUS SIBYNON, FITZ. 



GEN. CHAR. The generic characters, as derived from the species de- 

 scribed further on, are as follows : Supracephalic plates normal ; two 

 nasals ; no loral ; one anteorbital, or else one loral and no anteorbi- 

 tal; two postorbitals. Scales smooth, disposed upon fifteen longitudi- 

 nal series. Preanal scutella entire; subcaudal scutellae disposed 

 upon a double series. 



SYN. Sibynon, FITZ, Syst. Kept. I, 1843, 27. 

 Petalognathus, BUM. & BIBR. Erp. gen. VII, I, 1854, 463. 



OBSERV. This genus is one of the many subgenera into which 

 Fitzinger subdivides his genus DipsadomorpTms. The characters as- 

 signed to each by their author are, so far, left with us to conjecture. 

 The typical species is Coluber nebulatus, of Linnaeus, originally found 

 at Surinam, and subsequently in Mexico, and still more recently in 

 Peru. 



SIBYNON NEBULATUS, Fitz. 

 (Plate XI, figs. 11-16.) 



SPEC. CHAR. Body compressed. Prefrontal plates very small. Back 

 transversely black blotched, with a narrow white or yellow space 

 between the blotches, widening towards the sides, which are macu- 

 lated, as well as the abdomen. 



SYN. Coluber nebulatus, LINN. Mus. Adolph. Fred. 1754, 32, Tab. xxiv, fig. 1 ; 

 Syst. Nat. ed. X% I, 1758, 222 ; et ed. XII", I, 1766, 388. GMEL. Linn. Syst. Nat. 

 XIIL, I, iii, 1788, 1107. 



Coluber sibon, LINN. Syst. Nat. ed. X", I, 1758, 222; et ed. XII", I, 1766, 388. 

 GMEL. Linn. Syst. Nat. ed. XIII, I, iii, 1788, 1107. 



Sibon nebulatus, FITZ. N.. Class. Kept. 1826, 60. 



Dipsag nebulata, BOIE, in Oken's Isis, XX, 1827, 550. SCHLEG. Ess. Phys. Serp. 

 1, 1837, 162; & II, 275, PL xi, figs. 14 and 15. FILIPP. Bibliot. Italian. XCIX, 1840. 



Petaloynathus nebulatus, DUM. & BIBR. Erp gen. VII, i, 1854, 464. 



