DISCUSSION OF SPECIES ANI> THEIR DISTRIBUTION. 501 



Tentacle representing first dorsal tin retractile, with dilated trilobate tip. Soft dorsal 

 tin seven-rayed, inserted posterior to discaJ margin. 



Anal tin behind dorsal. Pectorals median, carpus narrow, slightly exserted, horizon- 

 tally placed. 



Ectoderm covered with numerous and strong stellular spines, above and below; the 

 spines being particularly strong and three pointed at. the margins of the disk. Tongue, air 

 bladder, and pyloric appendages wanting. 



DIBRANCHUS ATLANTICUS, Peters. (Figure 413.) 



Dibranchus atlantieus, Peters, Monatsberichte, Koniglich Preussischen Akademie, WIssenschaften, Berlin, 

 is?:, (76) 736), Coll, of H. M. S. Gazelle, coast of \V. Africa, lat. L0° 12' 9"N; Ion. 17° 25' 5" \V; depth, 

 360 fins.); plate with 5 il^s. — GOnther, Challenger Rep., xxu, 59. — Vaii.i.wi, Travailleur, 1888, :ii:i. 



Il.iln i<i,ui .•.fiilictisti, (ioooi:, l'l'oi'c.ediiigs U. .S. Xat. Mus., in (sig. L'!), Jan, 31, 1S81), 07. (Coll. of IT. S. P. 

 <_!., 1880, off Newport, R. I., depths 225 and 238 fins.), — Jordan and Gilbert, Bull, xvi, U. S. Nat. 

 Mus., 851. 



A species of Dibranchus with orbicular disk, nearly as wide as long; its length about 

 half that of the body; its lateral outline prolonged on each side, and terminating in a strong 

 spine, armed at the tip with a group of irregularly arranged acicular spinelets. Body cov- 

 ered above with numerous stout, conical spines with stellular bases. These are largest 

 upon the trunk, where they are approximately arranged in about four irregular longitudinal 

 rows upon each side of the dorsal fin. Closely set. rows of these stout spines mark the outer 

 margin of the disk, and there is also a cluster of live to seven upon each carpal peduncle. 

 Outside of these marginal spines, upon each side, is an irregular marginal row of five de- 

 pressed, knife-like spines, each tipped with a crown of three acircular spinelets. On the 

 anterior margin of the disk the two rows coalesce to a greater or less extent and form a 

 bristling array of closely set spines, some pointing dorsally, some laterally, some veutrally. 

 There are two kinds of spines upon the dorsal surface, in addition to the large ones already 

 described; some large,somewhat remote from each other, conical, stellular; others, much more 

 numerous and tilling the interspaces, prickle-like, stellular. Belly armed with numerous 

 closely set spines of a similar kind. Snout somewhat projecting, armed with three many- 

 tipped spines. A spine-armed ridge in front of the eyes, over the top of the snout. In this 

 4 spines are conspicuous, one in front of each eye, and between these alarger pair, in front 

 of the supraorbital ridges. From these last-mentioned spines extend spine-armed ridges 

 along the upper margins of each orbit. Under the snout is a cavity (horizontal diameter 

 i that of orbit) containing a barbel, pedicelled, with thick, club-shaped, trilobate tip. On 

 each side of this cavity are the nasal openings, which are as in Halieutichthys. 



The width of the mouth is equal to the distance between the centers of the pupils of 



the eyes. 



The diameter of the orbit is contained as follows in other dimensions of the body: In 

 total length, 9i; in distance from snout to dorsal, (I; same to anal, 7; the base of ventrals, 

 .">; to angle between pectorals and trunk, ~>S ; to gill opening, 5; in greatest width of disk, 

 5J; of trunk, 1. Width of iuterorbital area in diameter of orbit, §. 



Dorsal tin with <> or 7 rays, tin; longest, (3d) l.V times diameter of orbit, and (i times in 

 total length. Anal tin inserted entirely behind dorsal, with 1 rays, the longest (3d) about 

 aslong as longest in dorsal tin. Ventral fins inserted nearly under middle of disk, a little 

 nearer to vent than to mandibular symphysis, with one rudimentary and five well developed 

 rays, increasing in length posteriorly, the last and longest li.V times in total. Distance 

 between ventral origins, 1.\ in total length. 



Pectorals with peduncles slightly exserted, bases included in common membrane, com- 

 posed of 13 to 15 rays, the longest (3d or 4th) t' r ; in total. 



Caudal fin rounded, consisting of 9 rays, all bifid or triad excepl the two external 

 ones: length of middle ray, about half that of trunk and exceeding that of the pectoral, 

 being contained t 1 times in total length. 



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