662 report— 1878. 



also in this are found a flattened carapace and similarly formed antennae and 

 pereipoda. The hinder part of the body is much narrower than the anterior ; and 

 the leaf-like appendage of the second pair of antennas is much enlarged. It forms 

 a link between the Scyllaridae on the one hand, and the Astacidae on the other." 



" It is very astonishing, indeed," says Willemoes-Suhm, "that, among all the 

 crustaceans known to us, Willemoesia approaches most closely the fossil Eryontidae. 

 If we compare, for example, our figure of W. crucifera with the figure of Eryon 

 aretiformis, and the description of the ' Tribu des Eryons' given by Milne-Edwards 

 (and probably taken especially from Desmarest's ' Crustaces Fossiles') we find most 

 striking resemblances between the two forms. In W. crucifera as well as in Eryon 

 the carapace has 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 incisions 

 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 then in Willemoesia ; 

 but the second pair of them has, according to Desmarest, ' une ecaille a3sez large, 

 ovoide et fortement echancree.' This is the chief difference between Eryon and the 

 Palinuridae, and the same in which Willemoesia also differs from that group." 



So much do the fossil and recent animals resemble each other that the dis- 

 coverer 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 Willemoesia is to 

 be seen in the fossil crustacean " 



" Eryon," 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 their presence 

 seems not to be beyond all doubt." And the lamented carciuologist of the expe- 

 dition 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 Eryontidae this new genus must take its 

 place, between the Astacidae and Palinuridse. 



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 Polyc/ieles as having a thin dermal structure, rudimentary eyes, 

 antennae 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 

 wanting ; four or five pairs of pereiopoda chelate in distinct species. 



In all other respects the descriptions of the two authors agree. . 



The Challenger collection contains specimens of this group from thirteen 

 different places ; and in every one I was able, upon close examination, to find the 

 eyes very distinct, though singularly situated. Moreover, there is a variation in 

 form and position that gives them a value in classification, particularly when taken 

 into consideration with the relative forms of the several pairs of pereiopoda. 



The dorsal surface of the several species of this group is flattened and de- 

 pressed, and the anterior margin is tolerably straight ; the central tooth, which is 

 sometimes single and sometimes double, is never directed forwards in the form of 

 a_ rostrum, but upwards and obliquely forwards. In the anterior margin on each 

 side there is a deep cleft in the dorsal surface, in which the eye with its peduncle 

 is lodged ; the anterior extremity, being directed forwards, outwards, and down- 

 wards, is covered over by the lateral projecting wings of the carapace. It appears 

 to have two points of vision, the one upwards by the dorsal surface, the other 

 downwards and outwards by the lens at the extremity of the peduncle. But 

 thesg several points are liable to vary in degree. In some the dorsal notch is 

 almost non-existent, in others it is very deep ; and it is by this variation, taken in 



