NO. 1782. STRUCTURE AND HABITS OF W0LFFISHE8—GILL. 165 



Genus LYCICHTHYS. 



Lydchthys Gill, Ann. Rec. Sci. and Ind. 1876, 1877, p. clxvii. 

 Anarrhichas, sp. auct. pi. 



Type. — Anarrliichas latifrons Steenstrup. 



Anarrhicliadids with a moderately elongated body, rudimentary 

 scales, dorsal fin regularly elevated and with its hindmost spines 

 especially stiffened. 



TeetJi acute or subacute; intermaxillary rather slender, curved and 

 about 4 in an outer row, smaller (about 6) in an inner row; mandibular 

 4 to 6 slightly enlarged in front, curved and with subacute summits; 

 well separated, acute and biserial or uniserial on sides; the dentary 

 ridge not inflected ; vomerinem. small patch much shorter than palatine, 

 subacute and well separated; palatine subacute, well separated and 

 biserial. 



HypopJiaryngeal teeth enlarged in an inner row and a few scattered 

 outside. 



BrancMostegal rays 7, 4 to inferior edge of ceratohyal, 1 to hinder 

 angle of ceratohyal and 2 to surface of epihyal near lower edge. 



Ossification incomplete, the appearance sponge-like. 



Cranial axis nearly rectilinear, the vomer being on the same line 

 as the parasphenoid. 



Parasphenoid rather wide and expanded sideward in front of 

 cerebral chamber. 



Postfrontal region rather depressed and broad between interorbital 

 region and supraoccipital. 



Splienotic and parietal bones separated only by regular suture and 

 meeting in a ridge. 



Suprascapula undivided and attached to the inner surface of the 

 periotic ridge. 



Actinosts (2 and 3) much contracted at middle. 



The genus thus defined is confined to the deep cold seas of the North- 

 ern Hemisphere and has apparently four very distinct species exhib- 

 iting quite a remarkable range of dental variation, so great indeed 

 as to call for the differentiation of one of them from the others to 

 represent a peculiar group, were we to adopt for this genus the prin- 

 ciples in vogue for most others. 



The relative differences of the species, so far as regards dental 

 characters, are indicated in the following dichotomous table: 



Key to species of Lydchthys. a 



a' . Mandibular teeth biserial; palatine and intermaxillary teeth numerous. 

 6'. Vomerine teeth enlarged and crowded, 

 c'. Vomerine teeth much enlarged and with flattened crowns, 7 or thereabouts, 

 palatine teeth of outer row (about 6-7) erect, elongated and conic; of inner 



« I hope later to be able to go into more detail respecting the species of Lydchthys. 



