388 OPHIDIID^. 



The dorsal fin commences immediately behind the vertical from 

 the root of the pectoral, and terminates at a distance from the caudal 

 which nearly equals the length of the latter fin or two-thirds of that 

 of the head. It is composed of simple articulated rays, the anterior 

 of which can be received in a shallow groove ; the middle are the 

 longest, lower than the body. The vent is situated midway between 

 the roots of the pectoral and of the caudal, and the anal commences 

 immediately behind it, terminating opposite the dorsal. Caudal 

 deeply forked, scaly at the base ; its length is three-quarters of that 

 of the head. The pectoral is inserted opposite the notch of the sub- 

 operculum, and its length equals the distance of the end of the oper- 

 culum from the pupil. 



The scales are arranged with great regularity, and much longer 

 than high ; their free surface is furrowed by concentric striae, and 

 by others radiating from the centre. Wherever the striae cross 

 each other, a minute nodule is produced ; the margin is finely lobate, 

 and the middle lobule is larger than the others, tooth-like. The 

 lateral line runs near the base of the dorsal, and is bent downwards 

 at the extremity of the tail, towards the middle of the caudal. 



Fifth Group. CONGROGADINA. 



No ventral fins whatever ; vent remote from the head ; gill-open- 

 ings of moderate width, the gill-membranes being united below the 

 throat, not attached to the isthmus. 



15. CONGROGADUS. 



Machaerium *, Richards. Ann. Sf Mag. Nat. Hist. 1843, xii. p. 175. 



Body elongate, compressed, eel-like, covered with very small scales ; 

 vertical fins united, long ; ventrals none. Cleft of the mouth of 

 moderate width, with the lower jaw prominent. Jaws vnth a single 

 series of small teeth, closely set ; palate smooth. Branchiostegals 

 six ; gill-openings of moderate width, gill-membranes united below 

 the throat, not attached to the isthmus ; gills four, a slit behind the 

 fourth; pseudobranchiie well developed. Vent remote from the head. 

 Air-bladder and pyloric appendages none. 



Australian and East Indian coasts. 



1. Congrogadus subducens. 



Machaerium subducens, Richards. Ann. i^Mag. Nat. Hist. 1843, xii. 



p. 175. pi. 6, and Vorj. Ereb. ^ Terr. Fish. p. 72. pi. 44. figs. 1-6. 

 reticulatum, Bleek. Banka, ii. p. 734. 



B. 6. D. 71. C. 10. A. 60-65. 

 The height of the body is three-fifths of the length of the head, 

 which is contained six times and a half to seven times in the total 

 length. The dorsal fin commences above the end of the pectoral. 



* Preoccupied. 



