ERYONICUS. 109 
below the antero-lateral angle of the carapace ; the anterior margin of the 
lobe, moreover, bears a prominent papilla, or tubercle. The ophthalmopoda 
are distinct even in the smallest of the “ Albatross” specimens, which meas- 
ures only nineteen millimeters in length (Plate XXX., Fig. 1°); 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 ophthalmic lobe is present in the young as in the adult. 
On the whole, the condition of the ophthalmic lobes in the immature Eryo- 
nicus approaches that of Willemoesia. 
The mouth parts of ryonicus 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. Zodl., X. 26, 27, Plate I1V., Figs. 21 
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 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 Eryontide, 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 papille. 
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 Polycheles upon which Spence 
Bate founded the genus Sfereomastis. 
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: Ist, 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 
antennx (phymacerite), which assumes the form of a long cylindrical rod, 
