THE COPEPOD GENUS PARANTHESSIUS — ILLG 397 



(although it is rather at the extreme of one of the trends of modifica- 

 tion pointed out above) , mandible, maxillule, maxillipeds of the two 

 sexes, and the remaining thoracic limbs (although here the exceptional 

 armature of the second segment of the fourth endopodite remains 

 unique). 



In P. anemoniae Claus some features that distinguish it markedly 

 from most members of the genus were included in the generic diagno- 

 sis. The maxilla is unique, the more distal of the two setae of the 

 terminal joint being enlarged to equal in dimension and arrangement 

 of ornamentation the terminal prolongation of the main mass of the 

 segment proper, which, further, has the appearance of being jointed 

 basally. It is very difficult to reconcile this structure with the 

 usual condition in lichomolgids, but Claus' description is supported 

 by an account of Canu (1898), which is accompanied by a figure 

 comparable to that presented with the original description. The 

 armature of the fourth endopodite of P. anemoniae also sets this form 

 apart from all others of the genus ; indeed, is remarkable among the 

 members of the family Lichomolgidae. The first segment (basal) 

 bears the usual seta distally placed on the medial margin. The sec- 

 ond segment bears two medial setae. All other species referred in the 

 present treatment to Paranthessius bear a single seta on this segment, 

 and this last condition is typical also of members of L'lchomolgus^ 

 Modiolicola, and Sahelliphilus^ genera perhaps most closely related 

 to Paranthessius. All members of the genus Anthessius have the 

 setae in question exactly like those of P. anemoniae, but in my esti- 

 mation Anthessius is so distinct from typical lichomolgids that I in- 

 cline to the establishment of a family, or at least a subfamily, for this 

 genus and its allies. In all other characteristics, P. anemoniae is a 

 lichomolgid without question, and I should consider it a dubious bene- 

 fit to single out the species for generic status. Moreover, the unusu- 

 ally wide range of variability among the representatives of the genus 

 should provide latitude for the reception of Claus' species. 



Diogenidium Edwards, 1891, was instituted apparently without 

 knowledge of the description of Paranthessius, although the author 

 acknowledges consultation with Claus on systematic points dealing 

 with other copepods described in the same paper. D. nasutum con- 

 forms well to the generalized characteristics of Paranthessius in its 

 present sense. Various details were not included in the description; 

 the mouth parts, for example, were dismissed as like those of Licho- 

 molgus. One slight inconsistency occurred — the generic diagnosis 

 cites an 8-segmented antennule, but the species description and the 

 illustrations present the antennule as 7-jointed. The characteristic 

 rostrum is present and well developed. The segmentation of the 

 fourth endopod is typical, and the character of three outgrowths on 



