REVISION OF THE FISH FAMILY LIPARIDAE 45 



The taxonomic value of the number of teeth has yet to be thoroughly 

 demonstrated. The writer counted the rows of teeth in the majority 

 of the species but neglected to investigate the amount of variation 

 within a species. It is possible that certain species may be separated 

 by the number of oblique rows of teeth. 



Gill slit. — The size and position of the gill slit are of great taxonomic 

 value and are utilized for distinguishing the species in both the keys 

 and descriptions. The gill slit, when small, is restricted to the side 

 of the head above the base of the pectoral fin. When large, the gill 

 slit extends down in front of the base of the pectoral but is never 

 confined to this region. The gUl slit varies in position from above 

 the pectoral to down in front of 16 or more pectoral rays. The size 

 of the gill slit varies little with age and within a species never varies 

 more than in front of four or five pectoral rays. As the gill slit is 

 constant in size and position for each species and has become modified 

 in a heterogenetic manner in the different branches of the genus, 

 it can be utilized to great advantage in distinguishing species. 



As we should expect, we find certain species, such as Liparis 

 herscTielinus , in which some specimens will have the gill slit above 

 the pectoral fin while others will have it extending down in front of 

 the upper pectoral rays, the normal condition being either above the 

 fin or extending down in front of two or three rays. In some speci- 

 mens the gill slit on one side will be above the fin and on the other 

 side extending down on front of the upper ray. Such specimens 

 are difficult to identify by this character. 



The gill slit is typically above the pectoral fin in the tide-pool 

 species. The deeper water species typically have a larger gill slit. 



Dorsal Jin.' — The dorsal fin presents three important specific char- 

 acters, the number of rays, presence or absence of the notch, and 

 the extent of the connection with the caudal fin. The number of 

 rays varies from 28 to 48. The number never varies more than 

 four or five within a species. The dorsal notch is more characteris- 

 tic of the shallow water than of the deep water species. The dorsal 

 may be free from the caudal or connected with three-fourths the 

 length of the latter. 



The dorsal notch has formerly been used to separate the genus 

 Neoliparis from Liparis. The notch, however, is not of specific 

 value in Liparis dennyi and hristolense and other species. The dorsal 

 notch is present in some specimens and absent from others. The 

 anterior dorsal rays in the specimen from which the notch is absent 

 do not increase regularly in length but are about equal and form a 

 horizontal outline. 



The dorsal notch apparently bears no relation to the unsegmented 

 rays. The number of unsegmented rays also appears to be inde- 

 pendent of age. The number of rays in front of the notch is seldom 



