64 Zoological Society : — 



prolongation. The caudal fin is truncate, and rather more than a 

 ninth of the total length. The tail is much compressed and atte- 

 nuate. The lateral line is a groove that forks above the opercle. 

 After the junction of the divisions it rises a little, and then falls gra- 

 dually ; but under the anterior portion of the second dorsal fin there 

 is a rapid descent, after which it is straight along the tail. 



The single example on which this species has been founded was 

 taken near Madeira, in the month of March, and is now in the 

 British Museum. Its dimensions, expressed in inches, are given in 

 the following table : — 



Total length . . 14^ 



Height under first dorsal 3| 



Thickness near base of pectorals 2 



Head ^ 



Eye, diameter ^-^ 



Mouth, width from side to side 1| 



Barbel, length ii 



First dorsal fin, distance from snout 3-^^^ 



, length of first ray 2^ 



, length of second ray 1^^ 



, length of last ray jj 



, base of fin J'^ 



Second dorsal, distance from firgt dorsal -^ 



, length of base si 



, height in front 1 -X 



Pectorals, distance from snout 4 



, length 2^0- 



, width of base -^ 



Ventrals, distance from tip of mandible, mouth open 2^^ 



, length 4 



Anal, distance from tip of mandible, mouth open . . 6i 



, height in front ll 



Caudal, length 11 



Tail, height behind second dorsal jt- 



Order ACANTHOPTERYGII, Cuv. 



Fam. Trichiurid^. 



Nesiarchus, gen. nov. 



Body elongate, covered with small scales. Cleft of mouth deep. 

 Several strong teeth in the jaws ; none on the palatine bones or the 

 vomer. First dorsal not extending to the second. No finlets behind 

 either the dorsal or anal fin. Perfect thoracic ventral fins present. 

 Caudal fin well developed. A dagger-shaped spine behind the vent. 

 No keel on the tail. One lateral line. Seven branchiostegal rays. 

 An air-bladder. Pyloric caeca in moderate number. 



This genus may be entered in the Synopsis of Trichiuroid genera, 

 given in the Cat. of the Brit. Mus. Collection, thus : — 



"Ventrals present : a dagger-shaped spine behind the vent." 



