50 



Cheilobranchus dorsalis. Richardson. 



Ch. Spec. Ch. nigrescenU-fuscus, lined mediand dorsali, 

 pinnisque dorsi et ani pallidis. 



Radii: — Br. 3; C. 9. 



Plate XXX., figs. 1—5. 



The Synhranchi hitherto described have the anal aper- 

 ture situated at the distance of more than two-thirds of the 

 whole length of the fish, from the end of the snout; cvlin- 

 dvical, or round and slightly tapering bodies, compressed 

 only at the tail; a swelling head; a mouth cleft beyond 

 the eye ; and they inhabit the warmer parts of the ocean. 

 We have now to desci'ibe a fish, possessing many of the 

 technical characters of Synhranchus, but with a head 

 almost as small as Leptocephalus, the body compressed 

 throughout, and the vent before the middle. Such a dif- 

 ference in form from that of the typical Synhranchi, can- 

 not but be attended with some dissimilarity in the habits 

 of the fish, and seems to justify the imposition of a new 

 generic or sub-generic name, though from the want of a 

 sufficient number of specimens, I am unable to describe 

 the anatomical structure with suflicient fulness and correct- 

 ness. The term Cheilohranchus is derived from xf'^"", 

 labruni in ambitum diico, and Ppayxta, and has reference to 

 a small peculiarity in .structure, which we have not ob- 

 served in the Synhranchi, viz., the existence of a little 

 roll or lip on the hinder edge of the gill-opening. 



Cheilobranchus. 



Forma compressa postice lineari-laiiceolata. 



Caput minimum ; rostro ohtusiusculo, maxillis (Bqualihus. 



Radii branchiostegi Ires. Apertura branchiarum unica, 



mediana, suh gutture. 

 Osculum terminale, rictu ante oculos desinenti. 

 Denies suhulati acuti vel ohlusi, una serie dispositi. 

 Pinnae dorsi et ani humiles, memhranaceoR non radiis 



sustentatcB cum pinnd caudcd radiatd coalescentes. 



PinncB pectoris nulla. 

 Linea lateralis porosa. Papilla genitahs minuta (fig. 5). 

 Squamaj minima vix oculo armato dignoscendee. 

 Intestina cceco parvulo munita. 



A very small head, sloping upwards from the rounded 

 snout, attains an equal width and height posteriorly, but is 

 still inferior in both these dimensions to the fore part of 

 the body. The thickness is greatest at the shoulder, from 

 whence it diminishes gradually to the extremity of the 

 tail ; the height of the body increases to a little behind 

 the anus, where it exceeds twice the thickness of the same 

 part. The hinder part is linear-lanceolate in profile, and 

 acute. 



Mouth tcrmhial, with equal jaws, and a very small gape, 

 not extending so far back as the eye. The upper jaw is, 

 perhaps, somewhat protractile, but this could not be clearly 

 made out. A single row of teeth runs round each jaw ; 

 eight on each limb. In very young specimens they are 

 subulate, and incurved at the tips, but in the largest, which 

 IS the one that is figured, they are obtuse, and nearly cy- 



lindrical. They are covered by the rather loose, but not 

 tumid lips. 



The nostrils are close above the tumid, lateral eyes ; 

 one immediately over the centre of the orbit, and the other, 

 which has a tubular orifice, over the anterior angle of the 

 eye. 



The gill-opening is a small transverse slit on the middle 

 of the throat, and distant from the tip of the lower jaw, 

 exactly a tenth of the entire length of the fish. There is 

 no division in the opening, and three slender gill-rays 

 support the membrane on each side. A transverse lip, 

 which rises above the adjoining integument, and has its 

 outer ends free, forms the posterior edge of the orifice, and 

 appears to be capable of closing it very completely, when 

 the inflected edge of the membrane is pressed against it. A 

 little more than a third of the whole length of the fish is 

 anterior to the anus. The dorsal and anal fins show more 

 conspicuously, from being much paler than the rest of the 

 fin. The anal reaches from the vent to the tip of the caudal, 

 and is broadest at about two-thirds of its length from the 

 vent. The dorsal is also highest in the same quarter, but 

 sinks to the level of the back before it comes opposite to 

 the anus, though a pale stripe is continued from it along 

 the middle of the back to the head. Not a vestige of a ray 

 can be discovered in these fins, nor did I, in making the ske- 

 leton of a small specimen, observe any traces of interspinous 

 bones, excejjt a single, flat, triangular one at the tip of the 

 tail. This supports nine jointed rays, which are not 

 branched. The united caudal, dorsal, and anal, form an 

 acute tip to the tail. 



A straight furrow runs from the head to the base of the 

 caudal, coincident with the spine, and pale lines sloping 

 backwards, ascend and descend from it to the margins of 

 the body, being apparently the tendinous divisions of the 

 muscles, as in Leptocephalus, the body being otherwise of 

 an uniformly dark liver-brown colour in the specimens, 

 whicli have been kept in spirits. The fins are of a much 

 paler brown. I have not been able to make out scales 

 satisfactorily, with a microscope of considerable power, but 

 with a single lens, of half an inch focus, the skin is seen 

 to be closely studded with little round pits, which, iiom 

 the way that they reflect prismatic rays of light, are most 

 probably formed by depressed, but extremely minute 

 scales. 



The skeleton of a small specimen contains seventy- 

 three vertebrae, of which twenty-one are abdominal. The 

 superior spinous processes increase very gradually in 

 length from the head to halfway between the vent and the 

 end of the tail, where they are tallest, after which they 

 diminish, giving the lanceolate form to the tail. The last 

 vertebra, small and conical, turns up a little at its tip, to 

 which an obcuneate interspinous bone is attached, for the 

 support of the caudal rays. The under spinous processes 

 posterior to the vent are similar to the upper ones. Each 

 of the abdominal vertebrae has two transverse processes, 

 which diminish in length as they recede from the head, 

 and all the vertebraj have a short acute process inclining 

 forwards from the upper anteriorpart of their bodies before 

 the origin of the upper spinous processes. The vertebrae 

 are of the usual hour-glass shape, and are fully ossified. 

 No interspinous bones were discovered, except the caudal 



