68 Papers from the Department of Marine Biology. 



Cryptochirus is like Hapalocarcinus, but the rudimentary exopod is 

 not present in the appendage of the second segment. It must also be 

 noted that in the third maxilliped the ischiopodite and the meropodite 

 are more expanded than in the latter genus. The third maxilliped of 

 Cryptochirus thus forms more of an operculum for the buccal region 

 than it does in its relative. The sieve mechanism (text-figure 16) is also 

 less developed, and altogether it can hardly be said to be so highly 

 modified as in the gall-forming crab ; this is no doubt due to the fact 

 that isolation in the gall and consequently a preliminary filtering of 

 the plankton at the gall apertures make it necessary to have as perfect 

 an apparatus as possible. 



THE HOSTS OF HAPALOCARCINUS AND CRYPTOCHIRUS. 



The names in brackets are those of the authors responsible for the 

 record. 



(1) Hapalocarcinus marsupialis Stimpson. 

 Pocillopora: 



P. ccespitosa Dana [Verrill, Hawaiian Islands; Potts, Murray Island]; 

 ? P. brevicornis Lam., P. elongata [Verrill, Ceylon]; P. sp. 

 [Semper and D. Graeffe, quoted by Semper]. 

 Seriatopora: 



S. hystrix [Semper, Philippines; Potts, Murray Island]; S. imbricata 

 [Bassett-Smith, China Seas] ; S. elegans ? probably identical with 

 S. hystrix [Caiman, Murray Island]. 

 Sideropora: 



S. palmata, S. digitata, [Semper, Philippines]. 

 Stylophora: 



S. raristella Dep. var wilsoni J. S. Gard. [Potts]. 

 Hapalocarcinus has also been recorded from Millepora by Hickson. 



(2) Cryptochirus Heller. 



C, coralliodytes Heller: 



Goniastrcea bournoni; Astrcea sp., Trachyphyllia sp. [Semper, Philip- 

 pines]; Trachyphyllia sp. [A. Agassi/, quoted by Semper, West 

 Indies]; Leptastrcea solida (Ed. and H.); Leptoria tennis, [Potts, 

 Minikoi] ; Hydnophora lobata [Potts, Port Sudan, Red Sea.] 



C. dimorphus Henderson. In "a large branching madrepore." 



