76 H. J. VAN CLEAVE 



Genus Rhadinorhynchus Liihe 191 1. 



The genus Rhadinorhynchus was created by LtJHE (191 1) to include the 

 single species Rhad. pristis which occurs in fishes, chiefly of the Mediterranean. 

 The addition of another species, Rhad. horridiis from Egypt, and the recogni- 

 tion of the phylogenetic relationship existing between these two species and 

 Linton's Echinogaster sagittifer, caused LtJHE (191 2) to suggest the possible 

 justification for recognition of a sub-family Rhadinorhynchinae. This sub-family 

 was definitely recognized by the present writer (Van Cleave, 191 8) in a paper 

 which placed three additional species from North America within the same 

 subfamily. 



Rhadinorhynchus selkirki, new species. 



(Figures i to 4.) 



Described from five females and one male preserved in alcohol. Females 

 14 to 20 mm. long and from 0,6 to 0,8 mm. in maximum diameter. Single 

 observed male 6 mm. long and 0,46 mm. in diameter. Proboscis long, cylin- 

 drical; 2 mm. or more in length and from o,a to 0,25 mm. in diameter; armed 

 with 12 (in one instance 14) longitudinal rows of about 24 hooks each. Hooks 

 on ventral surface (Fig. 4) much longer and heavier than corresponding hooks 

 on dorsal surface (Fig. 3). Hooks in adjacent rows alternating except at the 

 extreme base of proboscis where the basal hooks of all rows occur at approxim- 

 ately the same level thus forming a single circle of 12 hooks, each about 

 89 [i long. ^ 



Comparison of hook lengths on ventral and dorsal surfaces of proboscis of Rhad. selkirki 

 (hooks are numbered from base toward tip of proboscis. Lengths are in ix). 



I 2 3 4 5 6 7 8 9 10 II 12 13 14 15 16 



Ventral row 89 83 89 94 94 94 94 94 89 89 89 94 94 94 83 83 

 Dorsal row 89 53 53 53 60 60 60 65 65 65 65 71 71 71 65 65 



In preserved specimens proboscis protrudes toward ventral side of anterior 

 extremity at almost a right angle. Posterior region of body curved so that 

 dorsal surface lies on concave rather than the more usual position on convex 

 surface of body (Fig. i). 



Proboscis receptacle 2,5 to 3,8 mm. long, double walled, with the retractors 

 of the proboscis receptacle emerging from the posterior margin. 



Anterior region of body-proper provided with spines which are grouped 

 into two fields. The spines at the anterior extremity of the body-proper form 

 an irregular collar, the individual spines of which measure form 41 to 88 [i. 

 Immediately posterior to this collar is a region entirely devoid of spines. This 

 in turn is followed by an area bearing conspicuous spines (Fig. 2). In some 

 individuals spines of this region attain a length of 115 [x though they more 

 frequently measure from 45 to 95 [i. 



About 1,5 mm. from the anterior extremity of the body-proper there is 



