SCIENTIFIC SUMMARY. 
187 
although numerous in species, are all very similar and show no indi- 
cations of an alliance with the Macrura, such as the Shrimps and Lobsters. 
Among the West Indian dredgings, however, such intermediate forms seem 
to abound. Thus Pylocheles Agassizii is described as connecting the Hermit 
Crabs with the Thalassinidae ; the abdomen, instead of being soft and unsym- 
metrical as in the former, is composed of firm, regular rings, and terminated 
by a symmetrical fin. This animal lives in holes, the entrance to which it 
closes with its claws. In Mixtopagurus , the abdomen is more developed on 
the right than on the left side, and divided into seven joints, of which the 
first five are imperfectly calcified, and the last two large and hard. In 
Ostraconotus the carapace is coriaceous, and the abdomen so small that the 
female uses the legs of the fourth pair to hold her eggs ; the last joint but 
one in these limbs is widened into a palette forming a floor on which the eggs 
rest. Spiropagurus and Catapagurus have a very small, twisted abdomen 
which the animals lodge in small spiral shells, contrasting curiously with the 
much larger carapace and legs which remain exposed. Eupagurus discoidolis 
inhabits the tubular shells of Dentalium, the orifice of which it closes with 
its claws. Xylopagurus inhabits holes in fragments of wood and the cavities 
of reeds, rushes, &c. ; the cavities are open at both ends, and the Crustacean 
does not go into its dwelling tail foremost after the fashion of the Hermit 
Crabs, but crawls in and closes one aperture with its claws and the other 
with the end of the abdomen which is converted into an opercular shield. 
Among the Dromiidse there are numerous forms leading towards Homola 
and its allies, and the genus Homola itself is represented by two species, one 
of which appears to be identical with the Mediterranean II. spinifrons, thus 
furnishing a striking example of the wide distribution of animals inhabiting 
the great depths of the sea. The genus Cymopolia, of which one species in- 
habits the Mediterranean, possesses eight in the Caribbean Sea. The genus 
Ethusa, supposed to be peculiar to the Mediterranean, is also found in the 
American seas ; M. Milne-Edwards has described a species from the Florida 
reefs under the name of E. americana, but states that it differs from the 
Mediterranean E. mascarone only by characters of little importance. 
It is impossible to overrate the value of such results as the above, and M. 
Milne-Edwards is quite justified in commenting with some pride upon the 
important bearing which such investigations must have upon our conceptions 
of the system of Nature. As one instance of this, he indicates that the 
results of the Travailleur’s expedition of last year in the Bay of Biscay 
showed the existence, in close proximity on the Spanish coast and in 
the neighbouring deep water, of two distinct faunas belonging neither 
to the same time (geologically speaking) nor to the same climate ; and 
he specially calls the attention of geologists to this fact as showing that 
at the present day and in the same seas, there must be in course of for- 
mation deposits absolutely contemporaneous, but which will contain the 
remains of perfectly dissimilar animals. The littoral deposits will contain 
the types of higher organizations ; the deposits formed at great depths will 
contain creatures of a more ancient character, some of them presenting un- 
mistakable affinities with fossils of the secondary epoch, while others re- 
semble the larval forms of existing species. 
We are glad to learn that the success of last year’s expedition will induce 
