256 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 



Poey's description, that identification with M. nocturnum would be 

 highly improbable. The other lot (No. 6871) consists of a single 

 specimen which answers Poey's description closely and is here identi- 

 fied as the type of M, nocturnum. This conclusion is rendered the 

 more probable as Poey is known to have sent many of his types to 

 the Museum of Comparative Zoology. The specimen in hand is 69 mm. 

 long to the base of the caudal fin, and must have been between 85 and 

 90 mm. in entire length. Poey's type is said to be 95 mm. long, but 

 this discrepancy cannot be considered serious in view of Poey's known 

 inaccuracy in details, consequent in part upon the fact that his descrip- 

 tions were taken more or less from his drawings, instead of from the 

 type specimens, as was indeed done in the case of M. nocturnum. 



The type of Diaphus nocturnus has been compared directly with the 

 type of Lampanyctus lacerta Goode and Bean, and the two found iden- 

 tical. D. lacerta was described from the Gulf of Mexico, and is well 

 known from the Gulf Stream off the Eastern Coast of the United 

 States. Other Myctophids from the Gulf Stream were also known to 

 Poey, although he failed to describe them. Specimens of Myctophum 

 opalmum and M. remigerum were collected by him at Havana and sent 

 to the United States National Museum, where they still bear his manu- 

 script names. As the latter have never appeared in print, it will be best 

 not to give them currency. 



Below is given a detailed description of Diaphus nocturnus, drawn 

 from the type specimen : 



Measurements in hundredths of length to base of caudal. Length of head 

 30.5; diameter of orbit, 9; length of snout, 5; length of maxillary, 22; 

 greatest depth of body, 21 ; least depth of tail, 9 ; distance from tip of snout 

 to front of dorsal, 50 ; to ventrals, 46 ; to front of anal, 65 ; to adipose fin, 81. 



Dorsal with 14 rays, including all rudiments : anal, 15 ; ventrals with 8 

 fully developed rays and a short outer rudiment; pectorals, 12. Scales in 

 lateral line, 38. 



Head more compressed, the snout less blunt than in most species of this 

 genus. Mouth large, oblique, maxillary very little widened posteriorly, its 

 tip reaching posterior angle of cheeks. Posterior preopercular margin oblique. 

 Inner teeth in jaws longer than the outer teeth ; vomer toothless, the pala- 

 tines and pterygoids provided with wide bands which cover the greater part 

 of the roof of the mouth ; tongue and basibranchials toothed. Gill-rakers of 

 moderate length, strongly toothed, 6 -f- 1 + 13 in number on the outer arch. 



Origin of the dorsal fin slightly in advance of the ventrals; origin of anal 

 well behind last dorsal ray; adipose dorsal above last anal rays; both pec- 

 torals and ventrals broken so their length cannot be made out. Scales all fallen. 



