160 THE VOYAGE OF H.M.S. CHALLENGER. 



is enveloped in soft skin, wliicli is thickest and miicigerous on the snout ; no foramina 

 leading into the muciferoiis system can be distinguished. The nostrils lie immediately 

 in front of the eye. 



The thick end of the snout overlaps the mouth, which is horse-shoe-shaped, its lateral 

 cleft extending to the front margin of the eye. Barbel none. 



The branchial cleft extends from the upper end of the gill-cover far forwards, the 

 brauchiostegous membranes being free from each other. Gill-laminse well developed ; 

 gill-rakers rather short, soft, lanceolate. 



All the fins arc long-rayed. The dorsal fin has a rather broad base, the length of 

 which is about one-third of its distance from the end of the snout ; it is very high, its 

 longest rays being much longer than the head, and even exceeding the pectoral fin. As 

 regards the anal fin, the rays of its anterior portion are about equal to the depth of the tail, 

 but the posterior increase in length, and exceed much the gradually decreasing depth of the 

 tail. The pectorals have a narrow base, are longer than the head, and extend backwards 

 to the origin of the anal. The ventrals consist of two rays each, of which the longer is 

 bifid at the end, and nearly reaches the vent ; the shorter and inner is rudimentary. 



The fish is nearly transparent, with a brownish tint ; dorsal and pectoral fins and a 

 broad mai'sjin of the anal black. 



'&' 



I am indebted to M. Tegima of the Tokio Museum for a specimen of this extremely 

 rare fish, which does not seem to have been observed since it was described in the 

 Fauna Japonica. It is 9 inches long, and in a good state of preservation, except for a 

 certain degree of desiccation, which it has undergone in consequence of the action of the 

 spirit on the mucous layer with which it is covered. Our specimen diff"ers in the shape of 

 the fins from the figure given by Schlegel. Perhaps this is due to age, as the specimen 

 of the Dutch naturalist was considerably larger. 



Family Ple qronectid^.^ 



As far as our present knowledge goes. Flat-fishes are, unlike the Gadoids and Ophi- 

 dioids, but sparsely rejjresented in the deep sea, and have not yet reached to a depth of 



' For the sake of completeness I mention here a small Flat-fish, 72 mm. long, which was ohtainetl hy the U.S. Fish 

 Commission at depths of 86 and 115 fathoms, in lat. 40° 0' N., long. 70° 23' AV., and which has been described by Mr. 

 Brown Goode under the name of Thyris or Delothyris pellucidus (Proc. U.S. Nat. Miis., vol. iii. p. 344, 1 880 ; and p. 1 10, 

 1884), and which both he and Mr. Jordan regard as a larval form. As generic diagnosis the following description is 

 given : — " A genus of heterosome fishes, with soft, transparent, elongate body. Head very short (in the single species 

 contained about 5i times in total length of body). Mouth small, toothless. Eyes upon left side, close together, the 

 lower slightly in advance of the upper. Pectoral flu upon blind side shorter and with fewer rays than upon coloured 

 side. Ventrals crowded together upon median keel of body, their bases prolonged upon this keel. Dorsal fin com- 

 mences iu front of the eye upon the snout. Dorsal and anal rays simple. Caudal fin subsessile, almost confluent with 

 dorsal and anal. Scales very small, thin, easily detached. Dorsal line marked, straight. Body translucent, colourless 

 (except for three longitudinal stripes in the single species). The vertebra? can almost be counted through the flesh when 

 the fish is held up to the light, and the arrangement of the gills is clearly visible through the opercular bones." 



