40 



THREE CRUISES OF THE " BLAKE. 



Acanthodromia, which recalls from the shape of its carapace 

 fossil Crustacea characteristic of the secondary formation, and 

 Dicranodromia, are peculiar new genera of Dromidse inhabiting 

 depths of 100 to 200 fathoms ; while Homolopsis, with eyes 

 nearly atrophied, is, like Cymonomus just mentioned, a Medi- 

 terranean genus which has been found by the " Blake " in the 

 depths of the Caribbean. Homalodromia, a genus of the fam- 

 ily of Homolidse, is in some respects intermediate between it 

 and the Dromidse, two families thus far most distinct, and occurs 

 in greater depths, from 300 to 600 fathoms. 



Among the hermit-crabs (Paguroidea) the species thus far 

 known were very similar, the head and claws alone being hard 

 and calcareous, while the soft terminal parts of the abdomen 

 are in the littoral species tucked away for protection into all 



sorts of bodies, such as shells and 

 the like. It must be most difficult 

 often for the deep-water species to 

 find appropriate hiding-places, and 

 it is not astonishing that the 

 dredgings of the "Blake" have 

 brought to light a number of re- 

 markable new forms, whose char- 

 acteristics unite them with the 

 Macrura ; as, for instance, Pylo- 

 cheles Agassizii, which has a per- 

 fectly symmetrical tail. It lives in 

 cavities excavated in fragments of 

 stone formed of agglutinated sand. 

 It entirely fills the cavity, closing 

 the opening with the claws, which 

 form a perfect operculum. Xylo- 

 pagurus rectus (Fig. 233), a slen- 

 der hermit-crab, inhabits tubes ex- 

 rect, \. cavated in bits of wood (Fig. 234) 



(Milne-Edwards.) or the hollow stems of plants open 



Fig. 233. 



Fig. 234. 



previously known only from the North- the West Indian region were discovered 

 ern and Southern oceans. On the other off the New England coast, 

 hand, species previously known only from 



