Hapalocarcinus, the Gall-forming Crab, etc. 67 
THE AFFINITIES OF THE HAPALOCARCINID~. 
On this subject Calman writes as follows: 
“While the characters of Hapalocarcinus, as now described, show clearly 
that it must stand alongside Cryptochirus, they give little help towards settling 
the place of the two genera in the system. The position of the female genital 
apertures shows that they must be placed among the true Brachyura, although 
there are some curious resemblances to individual genera of the Anomura. 
Thus the endopod of the third maxillipeds resembles somewhat that of 
Porcellana, while the rudimentary exopod suggests a comparison with the 
Hippidea. The number and uniramous condition of the abdominal append- 
ages also agree, except for the absence of the sixth pair, with the last-named 
group. These resemblances, however, are balanced by numerous important 
differences, so that even were we to set aside the evidence of the genital open- 
ings it would be impossible to place the genera in any of the groups of Anomura. 
On the other hand, the characters of the third maxillipeds and of the abdominal 
appendages and the greatly enlarged buccal area are unlike anything found 
among the Brachyura. The resemblance to the Pinnotheride appears to be 
quite superficial.” 
My own opinion coincides almost exactly with that of Calman, but I 
am inclined to lay even less stress on the resemblances to the Anomura. 
The characters of the male are typically Brachyuran. The likeness 
between the third maxillipeds of Porcellana and Hapalocarcinus is 
due to a similar mode of feeding. I have dealt at length with two of the 
divergences from the Brachyuran type mentioned by Calman; and the 
third, the character of the abdominal appendages, is more nearly paral- 
leled by Pinnotheres amongst the Brachyura than by the Hippidea, as 
Calman suggests. But in spite of this fact I thoroughly agree that 
there is no near relationship between Hapalocarcinus and Pinnotheres. 
Calman says further with regard to this point: 
“In describing Hapalocarcinus, Stimpson noted its resemblance to Pinno- 
theres in the large size of the abdomen and the softness of the integument, 
and he stated that its systematic position was probably between Pinno- 
theres and Hymenosoma. Apart from the two points mentioned, there seems 
to be little in the characteristics of the species as now described to suggest 
affinity with the Pinnotheride, while the third maxillipeds are widely different 
in type from anything found in that group.” 
In Hapalocarcinus 2 there are three pairs of abdominal appendages, 
while Pinnotheres 2 possesses the normal number, four. There is, how- 
ever, in both a tendency to a complete suppression of the exopod, a 
tendency not exhibited in other Brachyura, so far as I know. 
The following statement of the appendages forms the basis for a 
more exact comparison: 
Segment. Hapalocarcinus, Pinnotheres. 
ee eee e ele ee eee eee eee eee ee ee seer eee eee ee eeeiese esse eeneseesreeseeeeeeseseeseresessense 
aS ciete arate Biramous, but exopod rudimentary...| Biramous, but exopod rudimentary. 
ei secr evs, cte OEPEA TOUS iso sree shear e cia cai iiicv ea: hess Biramous; exopod very well developed. 
Oe Uniramous oo. e es ie | Ona RMmoOus: 
non Ee BE SP es CERO Ro eT | Uniramous. 
