REPORT ON THE DEEP-SEA FISHES. 211 



with a parabolic anterior profile ; mandible tapering in front and not longer than the 

 upper jaw. 



The dentition in the upper as well as in the lower jaws consists of a single series of 

 rather small teeth, not very closely set, fixed, not depressible, subequal in size, only two 

 pairs in front of the lower jaw being somewhat larger and strongly curved. Only 

 the intermaxillary is toothed. The teeth on the palate are reduced to a short series of 

 five small closely set teeth, which are depressed inwards and backwards. 



The gill-cover is so narrow as to leave a considerable portion of the gills uncovered. 

 The gill-laminas are developed, except on the hinder part of the horizontal branch of the 

 outer branchial arch, where they are remarkably short ; gill-rakers absent. 



A narrow bridge of skin behind the s}Tnphysis stretches from one mandible to the 

 other. Barbel small, tapering, about one-third of the length of the head, suspended from 

 the hyoid. 



The vent is placed very far backwards, its distance from the root of the caudal being 

 a little less than the length of the head. The anal fin extends nearly to the caudal, a' 

 little further backwards than the dorsal, the origin of which is opposite to that of the 

 anal. Behind these fins the tail is suddenly narrowed and terminates in a small bilobed 

 caudal fin. Pectoral fin rudimentary, its short rays being free at the tip. Ventrals 

 twice as distant from the eye as from the vent ; they are well developed, have a 

 moderately broad base, and are half as long as the head. 



The skin is rather tough, scaleless, but rhombic lines are visible, especially on the 

 side of the back, indicating the first commencement of the development of scales. The 

 luminous organs ^ are arranged thus : — 



a. A series of three or four minute eye-like spots on each side of the isthmus. 

 After a short interruption this series is continued along the abdomen by three similar 

 organs in front of the pectoral, by sixteen between the pectoral and ventral, and by 

 fourteen or sixteen between the ventral and anal. 



h. The lateral ventral series consists of similar organs, but still more minute in size, 

 and more or less disappearing at the level of the anal fin. 



c. A vertical series of three much larger eye-like organs on the gill-cover ; they do 

 not possess the white centre of those described hitherto, but appear through a rather 

 opaque round cornea-like membrane. 



d. The large suboeular organ which consists of two portions, one being elongate, as 

 long as the eye and lying close to the intermaxillary ; the other much shorter, between 

 the anterior end of the former and the front margin of the eye. Each of these organs 

 is of a pure white colour, has free margins all round, and lies in a hollow of the skin of 

 corresponding shape. 



Colour uniform deep black. 



' The histology of these organs is described in Appendix B. 



