1 02 Memoir Sears Foundation for Marine Research 



4 b. Dorsal base completely in front of pelvic bases ; first dorsal ray much 



prolonged. Chauliodontidae, specimens up 



to about 50 mm long,^^ Part 4. 

 3 b. Dorsal fin opposite anal, its origin far posterior to midlength of 

 trunk. 



5 a. Sides of body with scales, or marked by hexagonal pigment patterns 



resembling scales. Stomiatidae, Part 4. 



5 b. Sides of body scaleless, either unmarked or with parallel vertical 

 lines, never with hexagonal areas. 



6 a. Dorsal fin with more than 50 rays and beginning well before 

 middle of body; base of each dorsal and anal ray flanked on 

 either side by a sharp bony spur that penetrates the skin; length 

 of trunk posterior to head more than 20 times greater than great- 

 est depth of body. Idiacanthidae in part (adults), Part 4.^* 

 6 b. Dorsal fin with 30 rays or less, its origin well behind middle 

 of body; no bony spurs flanking bases of dorsal and anal rays; 

 length of trunk posterior to head not more than 1 5 times greater 

 than greatest depth of body. 



7a. Mouth with a membranous floor; isthmus attached to man- 

 dibular symphysis; dorsal corner of gill opening behind 

 posterior margin of eye. Melanostomiatidae, Part 4. 



7b. Mouth without a floor; isthmus attached to mandibular 

 symphysis by a muscular cord; dorsal corner of gill opening 

 above or in advance of posterior margin of eye. 



Malacosteidae in part, Part 4.^^ 

 2 b. Chin without fleshy barbel. 



8 a. Each shoulder with a tubular papilla open at the tip and connected 

 to a voluminous sac beneath skin. Searsiidae, Part 3, p. 254. 



8 b. Shoulders without tubular papilla or sac beneath skin. 



9 a. Dorsal fin preceded by the protruding, spine-like tips of from one 

 to several of the neural processes of a like number of vertebrae. 



Sternoptychidae, Part 4. 

 9 b. Dorsal fin not preceded by the protruding spine-like tips of the 

 neural processes of any vertebrae. 



10 a. Branchiostegal rays plate-like, conspicuously exposed, the up- 

 permost connected to subopercular and interopercular bones. 



Bathylaconidae, Part 4. 

 lob. Branchiostegal rays not plate-like, the uppermost not connected 

 to subopercular and interopercular bones. 

 1 1 a. Dorsal adipose fin present. 



53. For larger specimens, see Key C, 12 a. 54. See also Key D, i b. 



55. See also Key C, 15 b. 



