548 Memoir Sears Foundation for Marine Research 



preceded by a low fleshy ridge distinguishable forward to a point about opposite the 

 beginning of the last third of second dorsal fin. Pelvic fins with weakly convex anterior 

 and distal margins, subangular outer corners and gradually rounded posterior (inner) 

 corners ; length of pelvics along anterior margin about as great as distance from tip of 

 snout to middle of eye; origin posterior to axils of pectorals by a distance about equal 

 to that from tip of snout to origin of pectorals. Pectoral fins about Vs as long as distance 

 from tip of snout to opposite rear end of second dorsal fin; tips, when laid back, extend- 

 ing just beyond bases of pelvics; anterior margin weakly convex; distal margin straight 

 or slightly concave; apex sharp-pointed; inner corner broadly rounded. 



Prepelvic openings present. Frontal tenaculum embedded in skin in our immature 

 males. Claspers bifid but may develop as trifid with age. The female closely resembles 

 the male but lacks the prepelvic openings and, of course, the frontal tenaculum. 



Color. Dark brownish everywhere on head and body above and below; fins some- 

 what darker. 



Occurrence. Nothing is known of its habits except that, like most species of 

 chimaerids, it lives in deep water. It is known only from the offing of Pensacola, Florida, 

 at a depth of 305 fathoms. 



Reference : 



Hydro/agus alberti Bigelow and Schroeder, J. Wash. Acad. Sci., 4.I, 195 1 : 390 (descr., ills., Gulf of Mexico). 



Family RHINOCHIMAERIDAE 



Characters. Snout long, pointed. Lower surface of head without groove running 

 around in front of nostrils. Dorsal spine free from first dorsal fin toward its tip. Second 

 dorsal fin much lower than first dorsal, its upper margin nearly straight in known 

 species. Caudal fin without definite lower anterior lobe, much broader below axis than 

 above in adults but about equally broad above and below in young; caudal axis not 

 bent upward. Anal fin separate from caudal in some species but not in others. Pectoral 

 and pelvic fins about as in Chimaeridae, the former much the larger. Gums in upper jaw 

 smooth, without transverse ridges. Surfaces of dental plates smooth in some but with 

 a complex pattern of ridges and rounded prominences in others. Tongue with small 

 papillae. Lateral mucous canal an open groove, its longitudinal opening a narrow slit; 

 angular canal meeting oral canal some distance downward from point of junction of oral 

 canal with orbital canal (Fig. 124 A). Skin of trunk entirely naked on adults, but some, 

 when newly hatched, with a double row of strong denticles along midline of back that 

 disappear with growth (p. 552); upper margin of caudal with a crest-like development 

 of larger and smaller denticles in some (Fig. 122). Claspers of mature males simple, 

 slender, rod-like, with single terminal cartilage, the tip dilated «* and with numerous 

 small erectile thorns pointing toward the base, the shaft smooth or with low knobs. 

 Lower anterior surface of frontal tenaculum with ten or more hooked denticles pointing 



94. For further details as to the claspers, see Garman (Bull. Mus. comp. Zool. Harv., 41, 1904: 251). 



