194 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 105 



and anal fins comparatively long with several spines graduated in 

 size and many rays; pelvics i,6; caudal i,84-8,i; paired chin barbels 

 nearly as long as head; 4 branchiostegals; large ctenoid scales with 

 several rows of ctenii and about 4 to 6 radiating folds in basal region 

 but not reaching focus. 



The species of Polymixia are distinguished by the following key : 



la. Dorsal fin rays IV or V, 34 to 37, usually 36; total number of gill rakers 11 

 to 13, usually 11 or 12. Eastern Atlantic, Cuba .... P. nobilis Lowe 



lb. Dorsal fin rays V or VI, 26 to 32, usually 29; total number of gill rakers 14 

 to 21, usually 17 to 20. Western Atlantic P. lowei Giinther 



Ic. Dorsal fin rays V or VI, 29 to 35, usually 30; total number of gill rakers 12 

 to 14, usually 13. Western Pacific P. japonica Giinther 



It is not possible to distinguish the extreme variants of japonica 

 using the meristic characters of this key. The discussions in the 

 descriptions of each species give an interpretation of the possible 

 speciation and population divergence in the family. 



Polymixia nobilis Lowe 



Polymixia nobilis Lowe, 1836, p. 198, pi. 4 (type locality, Madeira). — Giinther, 

 1859, p. 17.— Goode and Bean, 1895, p. 243, fig. 241 (in part).— Fowler, 

 1936, p. 538, fig. 254. 



Nemobrama webbii Valenciennes, 1843, p. 41, pi. 8 (type locality, Canary Islands). 



Dinemus venusUis Poey, 1860, p. 161 (type locality, Cuba) (in part). 



Fourteen specimens ranging in standard length from 102 to 380 

 mm. were examined from the following localities: Madeira (8 speci- 

 mens), USNM 23324, CNHM 47977 and 47978, BM 1855.11.29.10 

 (holotype), 1862.4.22.17, 1862.4.22.18, and 1895.5.28.1, MCZ 31510;; 

 St. Helena (1 specimen), BM 1867.10.83; Cuba (5 specimens), MCZ 

 21812 (paratype of Dinemus venustus Poey, 191 mm. standard length), 

 and 4 specimens, MCZ 39168, from Atlantis Station 3439. 



Description: The characters distinguishing this species are the 

 greater number of soft dorsal fin rays, 36.1 : 34-37, and the lower num- 

 ber of gill rakers, 11.7: 11-13. The dorsal spines range from IV to V. 

 Other characters of lesser importance but showing interspecific dif- 

 ferences are: Soft anal rays 16.6: 16-18; pectoral rays 16.7: 16-18; 

 lateral line pores 33: 32-34; gill rakers short, longest raker 34 to 42 

 percent of diameter of orbit (table 7). A comparison of additional 

 characters with lowei and japonica is given in tables 4 and 6. 



In several specimens the dorsal fin was tipped with a prominent 

 black blotch; anal and caudal fins usually somewhat dusky; body 

 pale or dusky over a light silvery-gold; scales above lateral line area 

 with posterior portion blackish. The possibility of sexual dimorph- 

 ism in coloration could not be studied due to the few specimens and 

 their poor condition. 



