178 A HISTORY OF RECENT CRUSTACEA 
Diptichus, A. Milne-Edwards, 1880, the name Diptychus 
being pre-occupied. Of the species Uroptychus imsigms, 
Henderson, and Uroptychus gracilumanus, Henderson, figures 
are given on Plate VII. In this genus the second antennze 
have on the second (the first free) joint of the peduncle an 
acicle, thus differing from all the rest of the family, except 
Eumunida, in which one is also present, though of very 
small size. Dr. Henderson says :—‘ In those species which 
I have examined, the fifth arthrobranchia, counting from 
before backwards, is not of larger size than the others, 
whereas in most of the Galathodea it is distinctly en- 
larged.’ According to M. Jules Bonnier, in the species 
Uroptychus rubrovittatus (A. Milne-Edwards) there are no 
arthrobranchiz, their places being taken by a correspond- 
ing number of pleuro-branchiaze—that is, by branchie in- 
serted on the pleura or sides of the segments, instead of 
being placed on the articulating membranes that unite the 
appendages tothe segments. In this genus, and in Ptycho- 
gaster, A. Milne-Edwards, 1880, and in Humunida, there 
is a comparative weakness of the swimming-fan, which 
probably for that reason is twice folded on itself. The 
members of these genera being sometimes found in the 
branches of Gorgoniz, it is conjectured that they lead a 
sedentary life, that the swimming-fan is in consequence 
losing its importance, and an advance is thus being 
made towards the brachyuran type. Ptychogaster Mulne- 
Edwardsi, Henderson (see Plate VII.), from Patagonia, has 
the pleon, except the telson and uropods, covered with 
rows of short stout spines. 
The larval development in species of the genera 
Lithodes, Eupagurus, Anapagurus, Munidopsis, Galathea, 
Munida, and Porcellana, has been carefully studied by 
G. O. Sars, and his results confirm from this point of view 
the close union of the legions to which these genera re- 
spectively belong, as well as the propriety of including 
the whole group among the Macrura. From Sars’ work 
on this subject have beea borrowed the figures grouped 
together on Plate VIII., representing the end of the pleon 
in the last larval stage respectively of Lithodes maa 
