122 
“TERRA NOVA” EXPEDITION. 
and Ostraconotus *—may fairly be said to have become carciuized. It would be natural 
to expect that these three genera would be closely related, but, in fact, that is not the 
case. As regards the mode of reduction of the 
abdomen, Tylcispis and Ostraconotus do show 
some resemblance, though the process has been 
carried much further in the latter genus than in 
the former. In both of them the abdomen is 
straight and slender, and carries its unpaired limbs 
in the usual position on the ventral side. But 
when the appendages of the male are regarded it 
becomes evident that Tylaspis belongs to the 
group of genera which have paired limbs on the 
forepart of the abdomen (in point of fact it has 
two pairs), whereas Ostraconotus resembles Kupa- 
qurus in having no paired pleopods at all. The 
condition of Porcdlanopagurus in this respect is, 
as we have seen, at present still a little doubtful, 
but in any case, with its unique arrangement in 
the female of three limbs dorsally placed in a 
slanting row, it is obviously the result of an 
entirely different process from that which produced 
either of the others, so that, even if there were 
any grounds on which it could be supposed to be 
related to one of them, its carcinization must have 
Fig. 11. —Eupagurus splendescens 
outline dorsal view, x 2J-. 
occurred independently. The cephalothorax tells the same tale. In Tylaspis the soft 
hinder region found in an ordinary hermit-crab has become inflated and then 
hardened.f In Ostraconotus the whole cephalothorax has taken something of the 
shape of that of a Galatheid, the hinder region being hardened as in Tylaspis. In 
Porcdlanopagurus , while the hinder region remains soft, the 
forepart is quite unlike that of either of the others, as will be 
gathered from the description I have given of it. In the shape 
of the legs there is again the widest difference between the 
three. The sole point of resemblance between them lies in the 
fact that the last leg of each has the same minute, clumsy, 
3 
Pig. 12. — End of fourth 
leg of Tylaspis, X 7J-. 
spoon-fingered chela, and this they share with other Eupagurinae. The fourth leg is 
subchelate in Porcdlanopagurus-, simple, with a wide propodite for the protection of 
* For descriptions and figures of these crustaceans, see Henderson, “Challenger” Anomura, p. 81, 
pi. VIII, fig. 5, 1888 (Tylaspis), and Milne-Edwards and Bouvier, Mem. Mus. Harvard, XIV, iii, p. 167, 
pi. XII, 1893 (Ostraconotus). 
t This is also the case in Eupagurus splendescens. 
