114 University of Washington Publications in Biology [Vol.2. 



3b. A single external gill or opercular opening; the gills are covered by a 

 fleshy or bony covering, the operculum. 



15a. Gill cover composed of flesh or soft cartilage, not hard bones ; tail 

 tapers to a fine point ; skin without scales ; snout blunt ; teeth rat-like ; 

 1st dorsal with a long sharp spine. 

 Ratfish 15. Chimaeridae, p. 132 



15b. Gill cover bony, composed of opercular elements (bones). 



16a. (See 16b, p. 129.) Gill openings in front of or above base of pectoral 

 fin, never behind it ; no "bait" above on anterior part of head. 



17a. Dorsal fin preceded by short free spines, not connected by mem- 

 branes and none of which is developed into "bait" or luminous 

 organs, Fig. 6. 



Fig. 6. Free spines before the dorsal fin. 



18a. Pelvic fin with 1 spine and to 2 soft rays; 2 to 15 free spines 

 before the soft dorsal ; snout not prolonged and not tubular. 

 Sticklebacks 46. Gasterosteidae, p. 159 



18b. Pelvic fin with 1 spine and 4 soft rays; more than 15 spines 

 before the soft dorsal. 

 Many-spined Sticklebacks 47. Aulorhynchidae, p. 159 



17b. Dorsal fin not preceded by free spines, if spines are present these 

 connected by membranes except when specialized into long fila- 

 ments or into "bait." 



19a. (See 19b, p. 120, and 19c, p. 126.) Pelvic fins present, abdom- 

 inal in position, the pelvic girdle not connected by bones with 

 the pectoral or shoulder girdle. Fig. 7. 



20a. (See 20b, p. 117.) Dorsal fins 1 or 2 (the 2nd adipose) pres- 

 ent on back, finlets not included as these are detached soft 

 rays; if 1 dorsal fin is present, photophores are present. 



21a. (See 21b, p. 117.) The anterior dorsal fin composed of 

 rays ; the posterior fin chiefly adipose or if an adipose fin 

 is absent the body has photophores. 



22a. Body scaleless. 



23a. Head with barbels on chin and snout; teeth rather 

 small and not fang-like; pectorals each with a strong 

 spine. Fig. 8. 

 Catfishes 31. Ameiuridae, p. 150 



23b. No barbels on head ; dorsal fin long and high ; teeth 

 fang-like ; no spine in pectoral fin. 

 Lancet Fishes 34. Alepisauridae, p. 152 



