THE COPEPOD GENUS PARANTHESSIUS — ILLG 399 



lius) . He claimed importance for the rostrum as a generic character 

 but did not describe or illustrate the structure for any of the live 

 species that he otherwise completely depicted with his customary 

 meticulous care. 



The most important synthesis of the scattered synonymy of Paran- 

 thessius was offered by Monod and Dollfus (1932) in their survey of 

 the parasites of moUusks. They (pp. 143-146) refuted Canu's dif- 

 ferentiation of Herrmannella from Paranthesius^ pointing out parallel 

 extremes of variation in Lichomolgus and further demonstrating that 

 inclusion of Sars' Herrmannella species in the concept of the genus 

 broadens it amply to receive P. anemoniae. They also added Pseudo- 

 lichomolgus Pesta, 1909, to the synonymy of Paranthessius. 



The interpretations of Heegaard (1944) require comment with 

 reference to Paranthessius. This author's Scambicornus exhibits 

 many traits which come within the defined limits of Paranthessius. 

 Unfortunately, the types were not dissected, and the lack of informa- 

 tion about the mouth parts requires assigning the form as a genus 

 incerta sedis among the Lichomolgidae, if it belongs in that family, 

 as the author claims. As they are illustrated, admittedly somewhat 

 indefinitely, the mandible and maxilla of Scairibicornus are not like 

 those typical for the family Lichomolgidae. The fourth endopodite, 

 as depicted in the illustrations, has an armature that does not appear 

 elsewhere among lichomolgids. If these features could be clarified, 

 it seems possible that Scambicornus may be related to Paranthessius. 



More pertinent to present considerations on Paranthessius is the 

 invoking by Heegaard of the structure of the antenna of Herrmannella 

 prehensilis Sars, as figured by its author, in support of Heegaard's 

 proposition that such an antenna is a biramous appendage bearing an 

 exopodite and an endopodite. Sars' H. frehensilis has patently an 

 antenna in which the prehensile function has been transferred from 

 the stout claw typically borne on the terminal segment to a correspond- 

 ingly developed hooked spine on the penultimate segment, with the 

 end segment undergoing reduction to a short, palplike, setiferous 

 member. The illustrations in the original descriptions of H. seren- 

 dihica and H. robusta of Thompson and Scott ( 1903) are in agreement 

 with Sars' presentation. There seems to be no advantage in departing 

 from the traditional concept of the uniramous structure of the antenna. 

 The genus Paranthessius offers an array of species in which may be 

 traced verj' fully the tendency of transfer of prehensile function 

 from the ultimate segment to the penultimate. A further support to 

 the accepted view may be found in the condition of the antenna in 

 the family Clausidiidae where an expanded third segment with fairly 

 profuse ornamentation ordinarily dominates in size the more palplike 

 terminal segment. 



818707 — 49 2 



