KEY TO PHYLA 27 



41 (42) Abdominal segments provided with long lateral fil- 



aments of tufts of hair-like projections along either side, or 

 in some eases the last two abdominal segments only are sup- 

 plied with lateral rows of hair-like projections (see fig. 9) 

 ORDER COLEOPTERA (larvae) 



42 (41) Abdomen ending in a median non-segmented, tail-like 



process order neuroptera (larvae in part) 



43 (36) Mouth parts in the form of a jointed beak directed 



backward between the bases of the forelegs, often closely 

 applied to body order hemiptera (nymphs) 



44 (1) Head provided with two pairs of antennae in addition 



to an}^ feeler-like organs which occur in the region immedi- 

 ately around the mouth opening. " Never with wings. Res- 

 piration by means of gills, or in some small forms directly 

 through the skin. Mostly aquatic, class Crustacea.... 45 



45 (50) With a bivalve shell hinged along dorsal surface, cov- 



ering at least part of body and enclosing not only body w^all 

 but also the appendages 46 



46 (49) Entire body, including appendages and head, enclosed 



in a shell; resembling a small mussel 47 



47 (48) With but two pairs of trunk appendages 



subclass ostracoda 



48 (47) With ten or more pairs of trunk appendages 



subclass phyllopoda, order branchiopoda 



49 (46) Bivalve shell covering only part of body and frequently 



ending posteriorly in a pointed spine. Head not enclosed 

 in the shell and bearing large, fringed antennae used in 

 swimming subclass phyllopoda, order cladocera 



50 (45) Body covering firm and shell-like but not a hinged, in- 



dependent continuous shell covering the body 51 



51 (58) Eyes paired 52 



52 (57) Head, thorax and abdomen all bearing appendages. 



SUBCLASS malacostraca 53 



