REPORT ON THE DEEP-SEA FISHES. 259 



the lateral suspensory enlargements of the head is rather muscular. But the muscles 

 become attenuated further behind, forming a thin band on each side of the vertebral 

 column. A large abdominal bag, formed by the external integuments and the membranes 

 of the stomach, is suspended from the trunk, and may be so much distended that the 

 contents of the stomach are clearly visible through the walls of the bag. 



The trunk passes into the compressed tail, on which the muscles form only a 

 very thin layer. Gradually the depth of the tail diminishes, the last five inches being 

 as thin as a thread, in which at first elongate vertebral centra are still distinguishable, 

 whilst the last two and a half inches are a simple filament without segmentation. 



Fishes with the organs of locomotion so feebly developed, and with a long caudal 

 appendage which must be an impediment rather than a help in locomotion, may be 

 justly supposed to be sluggish in their movements, habitually lying on the bottom of 

 the sea, more or less concealed in the ooze. They patiently wait for the approach of 

 their prey, the size of which will compensate for the rarity of the occasions on which 

 a fish comes within their reach. 



The rupture of the abdominal sac has afforded an opportunity of examining some 

 of the vertebrae in the middle of the trunk. The fibrous ligaments connecting the 

 vertebrae are extremely thin, and as easily ruptured as in a well -macerated skeleton. 

 The centra of these vertebrae (fig. v) are 5^ mm. long, hour-glass-shajDed, with deep and 

 spacious concavities which are connected by a very narrow canal. A pair of short, acute 

 divergent spines start from the neural surface of the most constricted portion of the 

 centrum ; they project at a right angle from the longitudinal axis of the vertebra. On 

 the haemal side another pair of spines project, but they are directed backwards, and start 

 from behind the middle of the vertebra. The caudal vertebrae are shorter, as may be 

 seen through the skin, and become elongate again towards the narrowest portion of the 

 tail. 



It is difiicult in our specimen to fix the exact position and shape of the gill-openings. 

 They are longitudinal slits, eight or nine lines long, close together at the lower side of 

 the abdominal bag, and about one inch behind the angle of the lower jaw. There is 

 no separate gill-cavity ; a large body passing through the pharynx can be seen through 

 the gill-opening, which in consequence of the distension of these parts, would be a wide 

 open aperture. Three of the branchial arches stretch across the gill-opening, and are 

 more or less visible from the outside ; they are extremely slender, merely thin carti- 

 laginous rods with an indistinct knee-shaped bend, and with the gill-laminae less 

 developed than I have seen in any fish. The second branchial arch is hidden below 

 the skin, and still smaller than the posterior, the first being cpiite rudimentary, without 



any gill. 



The dorsal and anal fins are in a rudimentary condition. The former commences 

 in front of the vent, but its anterior rays become visible only by dissection, and with 



