166 A HISTORY OF RECENT CRUSTACEA 
The genus Ostracondtus, A. Milne-Edwards, 1880, and 
Tylaspis, Henderson, 1885, require notice, because, unlike 
all other Paguride, 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 2,575 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 1t 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 Sympaqurus, 8. I. Smith, 1883. 
The last-named genus, though belonging to the phyllo- 
branchiate Pagurids, nevertheless shows a slight tendency 
in the formation of the branchiz to agree with the next 
family. 
Family 3.—Parapaguride. 
The definition is the same as that of the Paguridee, 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 trichobranchie, 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 Paguride the stem gives rise to two rows 
of flattened leaflets.’ 
Parapagurus, 8. 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 
Hupagurus in having the third mayillipeds widely separated 
