CRUSTACEA MALACOSTRACA. III. 



besides, never developed as such plates as in Cymothoidae or Idotheidae, though sometimes they possess 

 an epimeral process. Finally I have discovered the praecoxa of the maxillipeds well preserved in a 

 couple of genera (see p. 9) but this joint has hitherto not been found in any member of the Malaeo- 

 straca, excepting Nebalia, while it is highly developed, f. inst., in Apus. The combination of these 

 primitive features, together with the far from primary but very peculiar development of the two 

 anterior pairs of pleopods, remove the Asellota rather far from the other Isopoda; probably features 

 in inner anatomy or embryology may besides be found to show primary or aberrant characters. 



The quite small but very interesting sub-order Phreatoicidea cannot be discussed here. — The 

 families hitherto referred to the Flabellifera are kept together only by the development of their 

 abdominal limbs, but two of them, Gnathiidae and Anthuridse, differ much from the three other families: 

 Cyinothoidse (sens, lat), Serolidse and Sphaeromidae, which constitute a natural group. In spite of the 

 difficulties I have kept the Anthuridse in the sub-order, but found it necessary to remove the Gnathiidae, 

 establishing them as a new sub-order, the Gnathiidea, which even is placed after the Epicaridea, 

 because the faniilv Bopyridae of the latter sub-order differs considerably less from the Cymothoinse 

 among the Flabellifera than is the case with the family Gnathiidae, which in some features differs 

 extremely from all other Isopoda, and, which is of special importance, the most aberrant features found 

 in the structure, sexuel difference, and development of the Gnathiidae can scarcely be considered as 

 modifications due to parasitism. 



The sub-order Valvifera is a most natural group, and the animals are easily separated from 

 the Flabellifera in having the uropods developed as a folding-door covering the pleopods. But whether 

 this single feature can be considered of a value sufficient for separating animals as the Idotheidse etc. 

 from the Flabellifera is very doubtful and no other external character can be pointed out. Whether 

 any internal character for the Valvifera can be found is questionable; if not, this sub-order may probably 

 be suppressed in a future ameliorated classification. 



The sub-order Oniscoidea cannot be discussed here; yet it may be pointed out that the family 

 Tylidae differs considerably from the others. — The Epicaridea are a most natural sub-order, but the 

 distance between it and some of the Flabellifera is, as already mentioned, not very great. 



It has been mentioned that I have now discovered the hitherto unknown praecoxa in maxilli- 

 peds in two genera of Asellota. In two genera of the group Munnopsini I found an interesting fusion 

 along the median line of the second pair of pleopods in the male. In Ligia I have found the praecoxa 

 and the squama in the antennae; in a few types belonging to Cymothoidae and Valvifera three joints 

 in the sympod of first pair of pleopods are pointed out. In Calatlutra brachiata Stimps. an unpaired, 

 probably sensory, organ has been found in the telson; in species of the genus Macrostylis a pair of 

 organs, probably sensory, were discovered in the abdomen. These morphological and anatomical features 

 are only briefly enumerated; readers taking interest in them may find them described later on in the 

 remarks on their sub-order, or in the descriptions of the genera or species in question. 



C. Geographical and bathymetrical Distribution. 



A restricted number of the forms are either decidedly, or most probably, pelagic, viz. Eurycopc 

 Murray! Walk., Paramunnopsis oceanica Tatt, Munnopsoides eximius n. sp., Pseudomunnopsis Beddardt 



