REPORT ON THE PELAGIC FISHES. 33 



Diplophos pacificus, n. sp. (PI. IV. fio-. B). 



D. 12. A. 53. P. 9. V. 7. 



The length of the head is oue-fifth of the total length, the greatest depth one-tenth. 

 Snout thrice as long as the eye, and the maxillary extending far behind the eye, nearly to 

 the prajopercular angle ; eye one-seventh or one-eighth of the length of the head. Cheek 

 covered by the enlarged suborbital bones. Dorsal fin higher than the body, its origin 

 nearer to the end of the snout than to the root of the caudal fin ; its last rays are 

 opposite to those of the anal. Anal extending to -nathin a short distance of the caudal 

 fin, its anterior rays are longest, but shorter than those of the dorsal; ventral fin rather 

 long, reaching to the origin of the dorsal fin, more than twice as remote from the pectoral 

 as from the dorsal. A singular spine-like projection opposite to the last anal ray may 

 be an accidentally detached portion of the root of the caudal fin, or represent a rudi- 

 mentary adipose fin. 



The phosphorescent organs are arranged as in Dii^lophos taenia, but are more 

 developed, having a silvery centre with a black ring, not only those of the main series 

 but also the smaller ones of the secondary series. Another series of small organs runs 

 along the middle of the side of the body and seems to be a specialized lateral line. 

 Other luminous organs, but very indistinct, can be seen on the hyoid bone. 



Brownish, with silvery lustre. 



A single young specimen of this interesting fish was obtained on September 2, 1875, 

 in Mid-Pacific (lat. 5° 54' N., long. 147° 2' W.), in the tow-net which had been attached 

 to the dredge. Although the dredge descended to a great depth, there is no doubt that 

 the specimen was obtained close to the surface ; it is 3 7 mm. long, that is, nearly of the 

 same length as the typical specimen of the Atlantic species. It had been mounted as a 

 microscopic preparation in glycerine, and has suffered considerably from this mode of 

 preservation. Although nearly of the same size as the types of the Atlantic species, it is 

 more advanced in development, as is evident from a comparison of the luminous organs. 



Fundulus nigrofasciatus, Lesueur. 



A specimen, 1 j inches long, was obtained on the jjassage from Tencrife to St. Thomas, 

 West. Indies, in the tow-net, in company with other pelagic surface fishes. 



The capture in mid-ocean of a species inhabiting the fresh and brackish waters of the 

 Atlantic States of North America is of great interest. It illustrates the way in which 

 reputed fresh-water species are spread to distant coasts by crossing wide expanses of 

 ocean. . The wide and irregular distribution of Cyprinodonts generally is probably to be 

 thus accounted for. 



(zooL. CHALL. EXP. — PAKT LXXVHi. — 1S89.) liii 5 



