178 A HISTORY OF RECENT CRUSTACEA 



Diptychus, A. Milne-Edwards, 1880, the name Dipti/chus 

 being pre-occupied. Of the species Uroptychus insignis, 

 Henderson, and Uroptychus gracilimamis, Henderson, figures 

 are given on Plate VII. In this genus the second antennas 

 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 

 arthrobranchias, their places being taken by a correspond- 

 ing number of pleuro-branchige that is, by branchiae in- 

 serted on the pleura or sides of the segments, instead of 

 being placed on the articulating membranes that unite the 

 appendages to the segments. In this genus, and in Pti/cho- 

 yaster, A. Milne-Edwards, 1880. and in Eumunida, there 

 is a comparative weakness of the swimming-fan, which 

 probably lor that reason is twice folded on itself. The 

 members of these genera being sometimes found in the 

 branches of Gorgonias, 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. Ptychog aster Milne- 

 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. 0. 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 been borrowed the figures grouped 

 together on Plate VIII., representing the end of the pleon 

 in the last larval stage respectively of Lithodes maia 



