260 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 



specimen, the scales of the lateral line are entire or very weakly armed 

 except in the middle where they are not concealed by the overlapping 

 scales, but other scales of the body bear short strong spines. 



The anal photophores are 7 + 4, the number most frequent in this 

 species. The two precaudals are near lower edge of caudal peduncle, not 

 more widely separated than the postero-anals, but somewhat obliquely 

 placed, the second a little higher than the first. The supra-anals form 

 an oblicjue line, very weakly angulated, the lower very slightly in 

 advance of the line joining the other two, the lower interspace about 

 half the upper. A minute antorbital photophore in its usual dorsal 

 position under the anterior frontal rim is evident in the young, but 

 becomes obscure and apparently functionless in adults. A larger antor- 

 bital photophore persists at lower anterior orbital margin, well below 

 the nostrils. The Mauritian specimen is a male with well developed 

 supracaudal luminous organ, consisting of four shining scales which 

 overlap little or not at all. 



The species differs from M. aspermn Richardson, according to the 

 original description and figure (Voyage " Erebus " and " Terror," Ichth., 

 p. 41, pi. 27, figs. 13, 15), in the larger eye, shorter snout, the fewer 

 anal photophores, and in the relative position of the supra-anals and the 

 precaudals, the former being strongly angulated and the latter widely 

 separated in M. asperum. The relation of M. pristilepis with M. opa- 

 linuni Goode and Bean is much closer. The two agree in general out- 

 lines and proportions, and in the arrangement of the photophores. In 

 M. opalinmn, the scales also are rough, a character which hitherto has 

 not been noticed, and which sei)arates M. ojmUnum widely from M. affine, 

 with which Brauer unites it. This statement is based on an examina- 

 tion of the types of M. opaHnu77i in the United States National Museum. 

 M. opalinmn has a much smaller eye and a somewhat longer snout than 

 M. pristilepis, and more numerous anal photophores, which vary from 

 8 + 5 to 9 4- 6. Even the lowest number known in M. op)aUnum is 

 thus beyond the known range of M. pristilepis, which is from 6 -^ 4 and 

 7 + 3 to 7 -f 5 and 8 -f 4. In all the respects in which M. opalinum 

 is known to differ from M. pristilepis, it approaches M. aspeincm. 



Myctophum humboldti (llisso). 



A specimen (No. 6870, M. C. Z.) collected by D. D. Roulet, " on a 

 voyage from China " answei's sufficiently well to the current descriptions 

 of this Mediterranean species, but these descriptions are so lacking in 

 detail that the identification cannot be considered reliable. Nor is it 



