PROMETHEUS ATLANTICUS. 145 



Within the group of large teeth in the upper, lying unfixed and moveable amongst 

 the loose skin at their base, may generally be discovered two or three replacement- 

 teeth, full sized, but yet unfixed by ossification of their base. These are provided 

 no doubt to supply the place of any sudden loss of the larger teeth : an accident to 

 which from their habits and the size and nature of their teeth these fishes must be 

 very liable. Both the vomer and the ethmoid are c^uite unarmed : the palatines are 

 furnished with a single row of small close-set teeth, like the edge of a fine saw. All 

 the teeth are slightly recurved. Thus the dentition is precisely that of Alepisaurus ; 

 resembling also that of Thyrsites in every respect except the unarmed vomer. 

 The tongue is free and pointed ; smooth behind, but rather rough in front with 

 several rows of small round whitish scabrous plates or flattened tubercles, like 

 nail-heads. The edges of the jaws or lips are thin and very even. The maxil- 

 laries are entire, simple, and rounded at the ends. 



Branchial openings very large, and extending considerably forwards : the mem- 

 brane is seven-rayed. The opercles like the cheeks and whole head are quite 

 plain, unarmed, thin, or membranous, and a little wavy at the edges ; that of 

 the preopercle being somewhat rivulose or veiny, whilst the opercle has a deep 

 broad notch or sinus just above the axil of the pectoral fin. The angle of the 

 preopercle is obtusely rounded. The humeral or scapulary bones are not per- 

 ceptible to the eye : the sides of the tail or fleshy base of the caudal fin are 

 simple, or without any keel ; and the whole fish is peculiarly plain in fomi and 

 structure. 



The first dorsal fin begins upon the nape, a little before the fore axil of the pec- 

 toral, and extends about two thirds the length of the body without the head or 

 caudal fin, along the back, ending opposite the vent. It is low, and nearly even 

 throughout : its height scarcely equaling half the depth below it of the body ; and 

 the rays, except the three or four last, being all of nearly equal length. They are 

 decided spines, but rather weak and slender ; the last is often very short, and 

 webbed down to the back behind. The web is excessively fragile or tender. 

 The base of the whole fin is seated in a groove. On the left side of the fish, 

 the fourth, sixth, eighth spines, and so on alternately, appear broader than the 

 rest. 



The second dorsal fin begins immediately behind the end of the first, but falling 

 short considerably of the base of the caudal fin, is much shorter in extent ; reach- 

 ing only two thirds of the remaining one third of the body. It is triangular, 

 aljruptly elevated in front, and somewhat higher than the first dorsal ; at its 

 higliest point its height is three fourths or four fifths of the depth of the body 

 beneath. Its two last rays are abruptly produced to twice or thrice the length of 

 the last one or two preceding : from which they are also detached by a space or 

 interval of one ray, and by a great sinus in the web, which is only connected to 

 the base of the foremost of the two ; though they are themselves webbed perfectly 

 together ; and thus they fonn a single two-rayed spurious finlet, the latter ray of 

 which is free or not webbed to the back behind, and longer than the first. 

 Though the connection of this finlet with the rest of the second dorsal fin is so 

 slight, yet it is raised a little whenever the hind rays of the latter are pulled for- 

 ward. The three first rays of this fin are simple and obscure ; but barred and 

 not pungent : the fourth or first branched ray is the longest. 



The anal fin is lower and smaller : but of equal length, and in every other 

 respect, particularly in its two-rayed spurious finlet, precisely resembling the 

 second dorsal. Its two first rays are simple but barred or flexible : the third or 

 first branched ray is the longest of all. Close before its origin are generally two, 

 almost detached and free, often extremely short, and generally inconspicuous, half- 

 buried spines : the first of which is sometimes reduced to a minute, triangular mere 



