166 A HISTORY OF RECENT CRUSTACEA 



The genus Ostraconotus, A. Milne-Edwards, 1880, and 

 Tylaspis, Henderson, 1885, require notice, because, unlike 

 all other Paguridae, they have the hinder part of the 

 carapace broad and firm, a character to which their names 

 ' shelly-back ' and ' callous shield ' make reference, whilst 

 they also have the pleon poorly developed. The species 

 Tylaspis anomala, Henderson (see Plate VII.), was dredged 

 by the Challenger in the mid-South Pacific, from a depth 

 of 2,375 fathoms, the greatest depth, as already mentioned, 

 at which any of the Anomala were found. This strange- 

 looking animal has the pleon not spirally twisted, and the 

 appendages of its sixth segment are almost symmetrical. 

 It is inferred therefore that it occupies some other dwell- 

 ing-place than a Gastropod shell. This species has in the 

 male a pair of genital appendages on each of the first two 

 segments of the pleon, agreeing in that particular with 

 Paguristes, Dana, 1852, and Sympagurus, S. I. Smith, 1883. 

 The last-named genus, though belonging to the phyllo- 

 braiichiate Pagurids, nevertheless shows a slight tendency 

 in the formation of the branchiae to agree with the next 

 family. 



Family 3. Parapaguridce. 



The definition is the same as that of the Paguridae, ex- 

 cept that the branchial plumes are filamentous. 



The species are marine and confined to deep water. 

 There are six genera. Dr. Henderson says : ' In all, the 

 gills are modified trichobranchias, each consisting of a cen- 

 tral stem which gives rise to two collateral rows of rounded 

 filaments, gradually decreasing in size towards the apex, 

 whereas in the Paguridas the stem gives rise to two rows 

 of flattened leaflets.' 



Pairapagurus, S. I. Smith, 1879, is typical of the ad- 

 vances made in recent years in submarine science, since a 

 genus so lately known now includes six species, together 

 covering in their range the whole breadth of ocean between 

 40 north latitude and 45 south. The genus agrees with 

 Eupagwus in having the third maxillipeds widely separated 



