20 BULLETIN 150, UNITED STATES NATIONAL MUSEUM 



described for Paraliparis memhraneceous . The rays are very fine and 

 the margin of the fin fringed. In some of the fragile forms the skin 

 connects with the rays some distance from their base. 



Pislc. — The disk reaches its greatest development among the tide- 

 pool species, where it is of most service to the individual. The average 

 for the number of times the disk is contained in the head in Liparis is 

 2.3 and in Careprodus 4.5. In Careprodus ostentwn the disk is of 

 minute size, yet perfect in structure. In Elassodiscus the disk is 

 minute and imperfect, the rays having been lost. This represents the 

 intermediate stage toward the loss of the disk. 



The disk is primitively flat. After it becomes functionless and 

 reduced in size it becomes cupped in some forms as in Careprodus 

 abbreviatus and the Careprodus colletti group. In some of these 

 cupped disks the margin is stiffened and the base set deeper into the 

 body. 



The shape of the disk is round or slightly oval and indented on the 

 sides anteriorly. In a number of species, as in the Careprodus 

 spedrum group and Careprodus rhodomelas, the disk is triangular. 

 This is due to the posterior margin being folded over and the sides, 

 anteriorly, being further indented or folded over. This condition 

 may represent the intermediate stage toward the cupped condition 

 as the completion of the folding over of the margin woidd produce 

 the cup. 



Vent. — One of the most striking modifications of a character in this 

 family is the change of position and direction of the vent. In some 

 species of Liparis the vent is nearer the anal fin than the disk. In this 

 genus and Careprodus the vent moves forward until it comes to be 

 situated at the posterior margin of the disk. In Paraliparis the vent 

 moves into the place once occupied by the disk. In Nedoliparis 

 it is on the throat in front of the symphysis of the pectoral. In all 

 the genera except Nedoliparis the vent opens downward. In the 

 latter genus the vent opens forward horizontally above a ridge on the 

 throat. 



Coloration. — The coloration in a general way is correlated with the 

 environment. The prevailing ground color of the tide-pool species 

 and their nearest relatives of the moderately deep water is brown, 

 olive, and slate; of the species from the region of little or no light 

 translucent, pink and black. The deeper-water forms range from 

 translucent to pure black in the greater depths. Light-colored 

 species exist far into the zone of darkness and certain species are 

 found both in the regions of little light and complete darkness. The 

 black species apparently are never found above 400 fathoms. Some 

 of the tide-pool species, as Liparis rutteri, are quite dark, but never 

 black. Light-colored species are taken from a black mud bottom, 

 but how far above the bottom they exist is unknown. 



