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. cespitosa Dana [Verrill, Hawaiian Islands; Potts, Murray Island]; 
? P. brevicornis Lam., P. elongata IV errill, 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 (Calman, Murray Island]. 
Sideropora: 
S. palmata, S. digitata, [Semper, Philippines]. 
Stylophora: 
S. raristella Dep. var wilsoni J. 8. Gard. [Potts]. 
Hapalocarcinus has also been recorded from Millepora by Hickson. 
(2) Cryptochirus Heller. 
C. coralliodytes Heller: 
Goniastrea bournoni; Astrea sp., Trachyphyllia sp. [Semper, Philip- 
pines]; Trachyphyllia sp. [A. Agassiz, quoted by Semper, West 
Indies]: Leptastrea solida (Ed. and H.); Leptoria tenuis, [Potts, 
Minikoi]; Hydnophora lobata [Potts, Port Sudan, Red Sea] 
C. dimorphus Henderson. In ‘‘a large branching madrepore.” 
