Willemoesla Group of Crustacea. 275 



as well as in Eryon the carapace lias nearly half the length of 

 the whole body ; and in both forms its lateral borders are 

 wing-like expansions which are divided by two deep inci- 

 sions into three portions. The anterior border of the carapace 

 is nearly straight in both forms. 



" Eryon was probably not blind ; for the eye-stalks have 

 been found in several specimens. Its antennae seem to be 

 somewhat more reduced than in Willemoesia ; but the second 

 pair of them has, according to Desmarest, ' une dcaille assez 

 large, ovoide et fortement dchancrde.' This is the chief dif- 

 ference between Eryon and the Palinurid^, and the same in 

 which Willemoesia also differs from that group." 



So much do the fossil and recent animals resemble each 

 other that the discoverer of the recent species says, " If the 

 last pair of pereiopoda and the pleon of Eryon were presented 

 to me I should undoubtedly declare them to be parts of the 

 genus Willemoesia. There are the same line of spines at the 

 top of the rings, the same wing-like expansions on both sides, 

 and that characteristic ' caudal apparatus.' Also the fine 

 fringe of hairs which distinguishes the caudal fin of Wil- 

 lemoesia is to be seen in the fossil crustacean." 



^^ EryoHj'' continues the same author, "differs from the living 

 genus chiefly by the presence of eye-stalks and of palpi at the 

 base of the gnathopoda. According to Quenstedt the latter 

 were observed only with difficulty ; and tlieir presence seems 

 not to be beyond all doubt." And the lamented carcinologist 

 of the expedition looked forward to his return, when he would 

 look over the original specimens and satisfy himself, so as to 

 enable him to give a more detailed account of the relations of 

 Willemoesia to Eryon. That they must be very close he 

 had no doubt, and considered that among the Eryontidse 

 this new genus must take its place, between the Astacidae and 

 Palinuridae. 



It will be desirable that we should examine the animals 

 and see how far the conclusions arrived at by two independent 

 observers can be supported by extended inquiry. 



Heller describes Polyclieles as having a thin dermal struc- 

 ture, rudimentary eyes, antennse like those of Willemoesia^ 

 and four pairs of pereiopoda chelate, and one (the fifth pair) 

 simple. 



Willemoes-Suhm describes Willemoesia as having the eyes 

 and eye-stalks entirely icanting ; four or five pairs of perei- 

 opoda chelate in distinct species. 



In all other respects the descriptions of the two authors 

 agree. 



The ' Challenger ' collection contains specimens of this 



19^ 



