CHORD. VIA 



28l 



Order 2. Holocephali 



The Holocephali (Gr. oXos, whole, and Kc<f>a\rj, head) have 

 long been placed in a subclass by themselves, owing to the 

 structural differences between them and the Selachii. But some 

 recent information concerning their development, taken together 



p cc . 



\ 



Fl<;. 290. A, Ckimcera monstrosa ; B, Callorkynckus antarcticus. a.cl, anterior clasper; 

 a.cl', pouch for its reception; br.ap, branchial aperture; c.f, caudal fin; c.f, its whiplike 

 prolongation; d.f.i, d.f.2, dorsal fins; fr.cl, frontal clasper; I./, l.f, labial folds; LI, 

 lateral line; na.ap, nasal aperture; op, operculum; pet./, pectoral fin; ptg, pterygopodia ; 

 pv.f, pelvic fin; /, teeth; tc, tactile flap; v.f, ventral fin. (A, after Cuvier; B, after 

 Parker and Haswell.) 



with their resemblances to the sharks, justify us in considering 

 them an order under the Elasmobranchii. There are only three 

 living genera, comprising about half a dozen species, and a few 

 extinct genera, and they are all marine. One genus, the Chi- 

 mrera, or sea cat (Fig. 290), occurs in Arctic and northern tem- 

 perate waters, one in the Antarctic and southern temperate 

 oceans, and one lives in the deep sea. 



