ERYONICUS. 109 



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

 lobe, moreover, bears a prominent papilla, or tubercle. The ophthahiiopoda 

 are distinct even in the smallest of the " Albatross " specimens, which meas- 

 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 antenna! peduncles 

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

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

 On the whole, the condition of the ophthalmic lobes in the immature Er>jo- 

 nicus approaches that of WiUemoesiu. 



The mouth parts of Eryonicus 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 Polycheles as described and figured 

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

 S. I. Smith in Bull. Mus. Comp. Zotil., X. 26, 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 simplj' 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 propodal 

 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 Enjontidoi, 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 papilla}. 

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

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

 abortive rudiments, as in those species of Poli/chclcs upon which Spence 

 Bate founded the genus Stereomasiis. 



Analysis reveals a close structural similarity between the genera Eryo- 

 nicus and Polycheles. The only important features distinguishing the former 

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

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

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

 antennge (phymacerite), which assumes the form of a long cylindrical rod. 



