MYCTOPIIOIDS. 249 



MYCTOPHOIDS. 



This group contains so many diver.se forms that it has been split up into 

 half a dozen families or more. Synodus, Chlorophthalinus, Benthosaurus, 

 Bathypterois, Ipnops, and Myctophum, each serves as the type of a family ; 

 and one or two of the other genera Avill no doubt on further acquaintance 

 be similarly utilized. As there is no apparent advantage for the present 

 report in the subdivision the group is here retained as a whole, though 

 given less extent than by some of the more conservative authors. The 

 Mj-ctophoids possess a very general marine distribution. "Wherever deep 

 sea collections have been made individuals of various species have proved 

 to be more or less abundant. Some forms are found near the surface, 

 probably nocturnal, others are certainly inhabitants of regions near the 

 bottom. Synodus, and species of Myctophum and of Chlorophthalmus are 

 fair instances from the upper levels of the ocean, and the bathjbial types 

 are instanced by other species of Myctophum and of Chlorophthalmus. and 

 by the genera Bathj-saurus, Bathypterois, Scopelengys, and Ipnops. Bathy- 

 saurus is credited with a vertical range of 1738 fathoms, going down from 

 a depth of 647 fathoms to one of 2385 ; the records for Chlorophthalmus 

 give a range of 1340 fathoms, between a depth of 85 and one of 1425 

 fathoms ; from the few captures made of Scopelengj'S its vertical range is 

 1137 fathoms, from G'J5 to 1832 fathoms; Ipnops has been taken at 1360 

 fathoms and at 1900, giving a range of 540 ; and Myctophum from the 

 records would appear to occur at all depths from the surface to 2620 

 fathoms. 



A considerable adaptive differentiation for life in the darkness obtains 

 among these fishes. Probably all of the known forms are more or less 

 luminous. The pos.session of lanterns, luminous glands or eye-like spots, 

 by many of the species suggests a natural subdivision of the group into 



