9 o Memoir Sears Foundation for Marine Research 



Typically the fins have no supporting spines,' most of the rays being branched; 

 however, in a few the rays are unbranched at the origin. Typically the pectorals* are 

 posterior to the gill openings, but in the genus Asquamiceps (Alepocephalidae) they are 

 well inside the gill cover; in the more primitive genera their line of insertion is low 

 down on the side near the ventral profile, but in some of the alepocephalids and argen- 

 tinoids they are inserted higher up on the sides; the pectoral bases are far below the 

 upper end of the gill openings except in some of the bathylagids, where the upper end 

 of the gill opening is greatly restricted. The pelvic fins,^ if present, are posterior to the 

 pectorals, their positions ranging from abdominal to thoracic. In most there is only one 

 dorsal fin with jointed bony or membranous rays (lacking in a few); in some there is 

 a fleshy "adipose" dorsal fin with unjointed horny rays between the rayed dorsal and 

 caudal fins; also, in a few (some Astronesthidae) there is a second adipose fin close in 

 front of the anus. The rayed dorsal, or the adipose dorsal if present, is separated from 

 the caudal by a definite gap, and in most the anal fin is similarly separated from the 

 caudal.' The caudal fin is about the same in width both above and below the projected 

 longitudinal axis of the trunk,' and the rear boundary of its fleshy base is symmetrical 

 relative to the axis of the trunk; in most, the rear outline of the caudal is more or less 

 deeply forked, or at least concave, but in some it is more nearly truncate transversely, 

 and in a few it is either rounded or has two or three of the middle rays extending almost 

 equally beyond the others (genus Pantodon). 



The radialia of the pectoral fins are articulated basally with the pectoral girdle. 

 In the great majority the pectoral girdle has a mesocoracoid element firmly attached 

 above to the auditory (otic) region of the skull (see also pp. 2, 6). In the pelvic fins 

 the basal radialia are reduced to a few small nodules, and the pelvics are not attached 

 to the pectoral girdle. The number of skeletal supports equals the number of rays in 

 the dorsal and anal fins. 



The head, though naked in the great majority, is clothed with smooth scales among 

 the Esocoidea and in the genus Lepogenys (Alepocephalidae) and with prickly scales 

 in Gonorhynchus\ in no living representative of the Order* is the head armored with bony 

 plates. And in no living family are the margins of the caudal fin armed with more than 

 one enlarged "fulcral" scale, such as is characteristic of the caudal of the sturgeons' 



3. Among the Idiacanthidae the base of each dorsal and anal ray bears on its anterior side a pair of short sharp 

 spurs that project through the skin (for details, see Beebe, 3: 152, 213). Among the Sternoptychidae, the rayed dorsal 

 is preceded by the projecting spine-like tips of approximately 1-7 of the neural processes of an equal number of 

 vertebrae (for an early account, see Cuvier and Valenciennes, 75: 395, 402, 419). 



4. The stomiatoid genera Idiacanthus, Photostomias, and Tactostoma (described by Bolin, 6: 39), are said to have no 

 pectorals; likewise some specimens of Eustomias and Photonectes. 



5. Among many families, such as the salmonids, specimens occasionally lack one or both pelvics, but this is an indi- 

 vidual anomaly (see Myers, 29: 600-601; 28: 41). 



6. Not in the freshwater Notopteridae of Africa and the East Indies, or in the genus Coilia (Engraulidae) of the 

 tropical warm-temperate Indo-Pacific. 



7. Most of the fin rays, however, are "attached to the lower spines of the hinder vertebrae, which are greatly 

 enlarged, and at the same time inclined backwards so as to be more or less parallel to the axis of the body" 

 (Norman, 31: 61). 



S. In the fossil Leptolepidae the dermal bones of the skull were covered with an enamel-like substance. 



9. These fulcral scales were "present, but usually small" among the fossil Pholidophoridae (Boulenger, 7: 545). 



