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108 



STALK-EYED CRUSTACEA 



Family ERYONTIDJE. 



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ERYONICUS Bate. 



Ann. Mag. Nat. Hist., 6th Ser., X. 456, 1882 ; Rep. Challenger Macrura, p. 122, 1888. lErT/oneicus:] 



The genus Eryonicus was established by Spcnce Bate for the reception of 

 a remarkable Erjonidj Eryonicus ccecm Bate^ secured during the voyage of 

 the " Challenger/' Feb. 11, 1873, off the Canary Islands, ostensibly from a 

 depth of 1620 fathoms. This specimen, which was only 13 mm.(i in.) long, 

 remained unique until 1890, when a similar specimen was captured in the 

 Bay of Bengal, 690-920 fathoms, by the naturalists of H. M. S. '^ Investi- 

 gator." The latter specimen, which was larger than the one obtained by 

 the ^'Challenger" (36 mm. long), was recorded but not described by Wood- 

 Mason in the Annals and Magazine of Natural History, 6th Series, VII. 

 199, 1891. Wood-Mason believed it to be an immature form of some species 

 of Pentacheles {Polycheks), as had already been suggested by Spence Bate. 



Eight specimens of Eryonicus were secured by the ''Albatross" in 1891, 

 the largest of which measures 62.5 mm. (nearly 2| in.) in length. With so 

 many and such large individuals at my disposal, I have been able to correct 

 some of the errors and supply some of the deficiencies in Spence Bate'^ 

 account of this interesting animal. 



The first abdominal somite, which was destitute of appendages in the 

 type described by Bate, in the largest of the "Albatross" specimens (a 

 male) bears a pair of limbs specialized for' sexual functions, very like the 

 corresponding appendages in the genus Polychdes. The inner branch of the 

 appendages of the second abdominal somite bears two processes (stylam- 

 blydes), as in the other genera of Enjordidoi. The first abdominal somite 

 of the female, also, carries a pair of less highly modified, simple, two-jointed 

 appendages. The existence of well developed external sexual organs, taken 

 in connection with the dimensions of the largest of the ''Albatross" speci- 

 mens, at once disposes of the theory that Eryonicus is an immature stage 

 in the development of some other genus. 



The ophthalmopoda, far from being absent in this genus, as Bate asserts, 

 present in the adult (see Plate XXX., Figs. 1, 1^, 1^) the same form and 

 dimensions as in the genus Polycheles. They consist of a large lobe, im- 

 movably fixed in a deep sinus in the anterior border of the carapace ; this 

 lobe sends forth an elongated cylindrical process outward and downward 



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