

EKYONICUS. 



109 



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below the antero-lateral angle of the carapace ; the anterior margin of the 

 lobcj moreover^ bears a prominent papilla^ or tubercle. The ophthalmopoda 

 are diatinct even m the smallest of the "Albatross" specimens^ which meas- 



m 



ures only nineteen millimeters in length (Plate XXX., Fig. I''); but here the 

 lobes are smaller, not filling the ophthalmic sinuses nor giving off the lateral 

 processes which^in the adult, project over the base of the antennal peduncles 

 beneath the antero-lateral angles of the carapace. The tubercle on the an- 

 terior margin of the ophthaluiic lobe is present in the young as in the adult. 

 On tlic whole, the condition of the ophthalmic lobes in the immature Er^o- 

 nicus approaches that of WlllcmocsicL 



The mouth parts of Enjonkm are for the "first time described and figured 

 on pp. 112, 113, and Plate XXIX., Figs. 2-2^ A comparison of these or- 

 gans with the corresponding organs in Polychdcs as described and figured 



by Spence Bate in his report on the "Challenger" Macrura, and by 

 S. I. Smith in Bull. Mus. Comp. Zool., X. 2G, 27, Plate IV., Figs. 2-7, 

 will show how closely they resemble each other in the two genera. 



In the largest male the fifth pair of legs is chelate, but the propodal digit 

 is only one half as long as the dactylus. In small, immature individuals the 

 propodal digit is undeveloped, the leg terminating simply in the dactylus. 

 In the largest of the females the chela of the fifth pair of legs is more per- 

 fect than in the male, owing to the greater relative length of the pjopodal 



digit. 



■ ; 



Spence Bate's description and illustration of the structure of the gills 

 apply to the immature stage only. In the adult the gills are similar to those 

 of the other genera of Eryonlidm^ consisting of a stem which gives off long, 

 very delicate lateral filaments ; the filaments decrease in length at the distal 

 end of the stem, until, near the very tip, they are reduced to mere papillae. 

 ^ The number and arrangement of the gills and epipods are exhibited in a 

 tabular form on page 114. The epipods arc for the most part reduced to 

 abortive rudiments, as in those species of Folfjclieles upon which Spence 

 Bate founded the genus StereommUs. 



Analysis reveals a close structural similarity between the genera Eri/o- 

 incus and Folyckeks. The only important features distinguishing the former 

 genus from the latter appear to be the folloAving : 1st, the great inflation of 

 the globular cephalo-thorax ; 2d, the compnratively small size of the abdo- 



r 



men ; 3d, the form of the process of the basal segment of the second pair of 

 antemuie (phymacerite), which assumes the form jof a long cylindrical rod, 



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