50 THE VOYAGE OF H.M.S. CHALLENGER. 



The Bathyhial Sea-devils which are noticed uudcr the following genera, are 

 degraded forms of Lophhis ; they descend to the greatest depths of the ocean. Their 

 bones are of an extremely light and thin texture, and frequently other parts of their 

 organisation, then- integuments, muscles, and intestines are equall)' loose in texture 

 when the specimens are brought to the surface. In their habits they proljably do not 

 difier in any degree from their surface representative, Lophiiis. 



When the first individuals of this group were discovered, they seemed to be 

 sufficiently distinct from one another to justify generic separation. However, the 

 additions of recent years exhibit that variation in the shape of the body, head and 

 mouth, in the specialised dorsal spines, and in the development of dermal scutes, which 

 may be expected in such grotesquely formed creatures ; and future discoveries may lead 

 to a further reduction of genera, "\nz., to the union of the naked-skinned Mdanocetus and 

 Oneirodes with Ceratias. 



The number of the dorsal spines is always reduced, and at the end of the series of 

 these fishes only one spine remains, with a simple, very small lamella at the extremity 

 {MelanocetUft joJuisonii, Melanocetus murrayi). In other forms sometimes a second 

 cephalic spine, sometimes a spine on the back of the trunk, is preserved. The first 

 cephalic spine always retains the original function of a lure for other marine creatures, 

 but to render it more efi'ective, a sj^ecial luminous organ ' is sometimes developed in 

 connection with the filaments with which its extremity is provided {Ceratias hispinosus, 

 Oneirodes eschrichtii). So far as is known at present, these complicated tentacles attain 

 to the highest degree of development in Iliniantolophus and Aega'onichthi/s. In other 

 species very peculiar dermal appendages are developed, either accompanying the spine 

 on the back, or replacing it ; they may be paired or form a group of three, are pear- 

 shaped, covered with the common skin, and perforated at the top, a delicate tentacle 

 sometimes issuing from the foramen. 



Himantolophus, Rhdt. 



Body, short, thick, moderately compressed ; head very large. Eyes rudimentarj-. 

 Mouth directed obliquely upwards, of moderate Avidth, with projecting mandible. Jaws 

 armed with several series of rasp-like depressible teeth of difi"erent lengths ; palate 

 toothless. Skin thick, with round scutes scattered over the body. The spinous dorsal 

 reduced to a single filament ; the soft dorsal and anal very short. Ventrals none. Gills 

 two and two halves. 



' Wliose function was first suggested by Ltitken. 



