REPORT ON THE DEEP-SEA FISHES. 23& 



scales; sc are the scales, which overlap each other only to a slight extent, the overlapping 

 ends being closely adpressed (not apart as shown in the diagram for the sake of clearness). 

 Each scale possesses a transverse ridge (?-), behind which the gland-like white substance 

 of the luminous organ (I) is lodged. A membrane (?) investing the greater part of 

 the transverse ridge (?'), and extends forwards covering the preceding scale until it 



arrives at the luminous organ, where it terminates in a free margin closely surrounding 

 the luminous organ. All these structures form the inner side of the canal (c), its 

 outer wall being formed by the outer membrane (m), which is irregularly interrupted 

 at the places marked 1, 2, 3, and 4. 



There are twenty-six luminous spots between the gill-opening and the vent, and 

 about as many behind the vent along the base of the anal fin. In order to show the 

 arrangement of the luminous organs on the head, it is necessary to remove the 

 integument which covers the muciferous bones. They then represent the disposition 

 shown in figs, a' and a". The organs are of the same shape and structure as on the 

 lateral line, about nine in number in the infraorbital canal. In the continuation of 

 this canal on the rostral process of the snout, three other pairs of luminous organs are 

 developed, and visible on the lower side of the rostrum after removal of the skin. 



The mandibulary canal contains five luminous organs, and is continued along the 

 lower portion of the much enlarged suboperculum. A large patch of a white substance, 

 which does not diflfer from that of the luminous organs described, is deposited in this 

 as well as the other species (with the exception of Halosaurxis owenii) in the upper 

 part of the gill-cavity, between the gills and the upper part of the supraclavicle. When 

 this substance is detached from the skin, the surface of the latter is seen to be covered 

 with a great number of minute papillae. ^ 



Halosaurus mediorostris, n. sp. (PL LIX. fig. C). 



B. 11. D. 11. V. 8. P. 8. L. transv. 11 | ?. 



Allied to Halosaurus macrochir and with the same comparatively short snout, but 

 with a shorter pectoral fin. The length of the prseoral portion is not quite one-third 



' An account of the histology of these luminous organs will be found in Appendix B. 



