But a perfectly unique structure in this fish ‘is a thin cylindrical muscular band which connects the back part of the mandibular symphysis with the hyoid bone. It is probably the homologue of a muscular band which, in other Stomiatids, stretches on each side from the mandible to the side of the hyoid, the two bands coalescing into an unpaired one in _Malacosteus_. It is, in the present state of preservation, much elongated, like a barbel, but during life it is notably contractile, and serves to give to the extremity of the mandible the requisite power of resistance when the fish has seized its prey, as without such a contrivance so long and slender a bone would yield to the force of its struggling victim.’ [Illustration: FIG. 22.—_Saccopharynx ampullaceus_; a deep-sea eel, with the head of a large fish, which it has swallowed, showing through the thin integuments of the body. (From Günther.)] Belonging to the family of the Salmons we find one genus _Bathylagus_ that is undoubtedly an abysmal form. Although there may be some doubt as to the exact depth at which the specimens were captured, the thinness of the bones, the enormous size of the eyes, and other bathybial characters prove that they must live in very deep water. Closely allied to the salmon and the herrings is the family of the Alepocephalidæ, a family that contributes several forms to the fauna of the deep sea, but they do not possess any characters that call for special comment. Their vertical distribution varies between 345 and 2,150 fathoms. The family Halosauridæ contains five species all confined to the abysmal zone. They have long bodies tapering to a finely pointed tail, and the head is provided with a snout that projects considerably in front of the mouth. Of the family of the Eels there are several representatives in the deep sea. They are characterised by a combination of true eel characters with special modifications due to a bathybial existence. ‘To enable them to seize upon prey more powerful than themselves certain organs have undergone a degree of specialisation, as is observed in bathybial members of other families with a similar mode of life; the jaws are exceedingly elongate and the whole gape, the pharynx and stomach capable of enormous distension.’ The head is very large, the eye very small and the tail long and tapering (fig. 22).