22 Crust. 
CRUSTACEA. 
group includes the Platyscelidce , Phorcidce , and Oxycephalidce of Spence 
Bate. Bovallius divides it into eight families, including the Oxycephalidce. 
These are defined as having the telson coalesced with the last ural seg- 
ment, and the seventh pair of pereiopoda complete, and not transformed. 
Bourne (3) considers Monstrilla to be a free-swimming and not a 
parasitic form. It may be an ephemeral reproducing form, with a pre- 
daceous larva, but the young forms taken by Norman scarcely support 
this view. 
The Monstrillidce may be classed as a subfamily of the Corycceidce. 
The genus Monstrilla is re-defined, and six species recognized. . 
VI. — GrEO GRAPHICAL DISTRIBUTION. 
General. 
Mayer deals with the geographical distribution of the Caprellidce on 
pp. 94-103 of his monograph. 
The distribution of freshwater Calanidec is discussed by de Guerne & 
Richard (4). 
Imiiof, 0. E. (3) enumerates 29 species and 4 varieties of the genus 
Bosmina. Only two of the species are extra-European, B. rnacrorhynca 
from Egypt, and B. striata from N. America. 
De Guerne & Richard exhibit, by means of a map and a tabulated 
list, the distribution of 77 species of freshwater Calanidce. Only one 
(Diaptomus) of the ten genera appears to be cosmopolitan. Six genera 
have been found in the northern hemisphere only. The Calanidce of the 
north seas are able to bear great cold, and much alteration in the saltness 
of the water. This seems particularly to have been the case with Biap- 
tomus. The freshwater are derived from the marine forms. 
British Isles. 
Crustacea taken off the S.W. of Ireland ; Bourne (1). 
Surface collections from the N. Sea, and from the W. of Scotland ; 
id. (2). 
Brachyura from Cornwall ; Cornish. 
Palaeozoic Ostracoda from Wales and Ireland ; Jones (1)1 
Some Crustacea from the Forth ; Scott. 
Copepoda from Liverpool Bay ; Thompson, J. C. 
European. 
Pelagic Crustacea from the G. of Marseilles ; Gourret. 
Terrestrial Isopocla of Marseilles ; Aubert, &c. 
JDecapoda from the G. of Naples ; Cano (2). 
Epicarklce from the G. of Naples ; Giard & Bonnier (2). 
Copepoda from the neighbourhood of Boulogne ; Canu (3). 
