156 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 9 



Family Dactyloscopidae 



Artificial Key to the Known Genera 



la. Dorsal fin continuous. 



2a. Dorsal origin on nape Dactyloscopus Gill 



2b. Dorsal origin far behind nape, over or behind anal opening. 

 3a. Head cuboid, bluntly truncated anteriorly; mouth vertical 



Dactylagnus Gill 



3b. Head elongate, acutely conical; mouth moderately oblique 



. Myxodagnus Gill 

 lb. Dorsal fin divided, anterior three or four spines separated from 

 rest of fin. 

 4a. Total number of dorsal spines XXH ; dorsal rays 19 to 20; 

 abdomen scaled over ventral mid-line before vent; two 

 anterior dorsal spines widely separated from the other dorsal 

 spines; head conical; snout sharp and pointed; arched part 

 of lateral line short .... Heteristius, new genus 

 4b. Total number of dorsal spines X to XIV ; dorsal rays 26 to 

 31; abdomen naked along ventral mid-line before vent; 

 dorsal spines evenly spaced. 

 5a. Arched and median portions of lateral line about equal ; a 

 separate anterior dorsal of three spines, first spine highest, 

 second and third spines shortened ; labial fringe absent on 

 upper lip, little evident on lower lip . . Gillellus Gilbert 

 5b. Arched portion of lateral line much shorter than median 

 portion ; a separate anterior dorsal of four short, well- 

 separated spines; labial fringe present on both lips . 



Cokeridia Meek and Hildebrand 



The Dactyloscopids form a small family of American marine shore 

 fishes. They closely resemble certain more or less distantly related Austra- 

 lian fishes, such as Crapatalus. The southernmost species, Gillellus aus- 

 tralis Fowler and Bean (1923, p. 23), is said to be from Valparaiso, 

 Chile, 2 although the family is primarily tropical in habitat. Most of the 

 species were described by T. N. Gill or C. H. Gilbert, and no modern 

 monograph of the group has appeared. The majority of the known fonns 

 are, however, treated by Jordan and Evermann ( 1898, pp. 2297-2305) or 



2 This locality record needs confirmation. The species is known only from the 

 types collected by the United States Exploring Expedition over 100 years ago, and 

 the subsequent history of the fish collection made by this expedition lays any 

 unusual record based on it open to suspicion. 



