liv INTRODUCTION. 
changes in the forms that the animals of this genus 
undergo in their growth to an adult state, it is not im- 
probable that immature specimens may be misinterpreted 
for adult varieties. Cyamus lives parasitically on the 
whale, and probably thrives on no other animal. The 
one or two solitary specimens that have been found 
attached to the dolphin are probably young creatures that 
have strayed from their natural habitat. 
The genera of Jsopoda appear to be more generally 
diffused throughout the various regions of the sea; and 
from the various distant localities in which that species 
have been found, some may be inclined to think that 
they are universally distributed. 
The genus Tanais has been found on the coasts of 
North-Western Europe, Brazil, in the Zooloo and Feejee 
seas, as well as on the western coast of North America ; 
and equally varied have been the recorded habitats of the 
nearly allied genera, Paratanais and Leptochelia, which 
latter Fritz Miller believes to be the male of Tanais. 
The near ally, Apseudes, is only known in Europe and 
Egypt, where but few specimens of two closely resem- 
bling species have been found. The genera Anthura and 
Paranthura are also sparsely represented, both in the 
species and specimens. They have been taken on the 
southern and western coasts of Europe, at New Zealand, 
the Mauritius, and the Cape of Good Hope, as well as on 
the eastern coast of North America. Of the genus Anceus, 
of which eleven species have been determined on the 
north-west coast of France, by M. Hesse, three at most 
are known to the rest of Europe, and but a single species 
to the eastern coast of North America. 
The Bopyride are tolerably abundant in the temperate 
regions, but few in the more tropical or Arctic latitudes, 
the genera confining themselves with considerable exacti- 
tude to peculiar species of Crustacea. Thus we have failed 
