406 GEOLOGICAL SURVEY OF THE TERRITORIES. 
back directly to the ancestral Nauplius, the common ancestor of all the 
Neocarida. 
Nor does it seem to us that this statement or hypothesis is weakened ~ 
when we consider the resemblances between the thoracic feet of the 
Phyllopods and the maxille and maxillipedes of the Decapoda. When 
we compire the leg of a Phylopod with the , 
second maxille* of the lobster or cray-fish, we 
can detect a close homology, the chief difference 
being in the fact that the lobes of the endopo- 
dite are less numerous in the Decapod than in , 
the Phyllopod. This close resemblance is based 
on the fact, which appears to have been over- csieenE. 
looked by Claus and Lankester, 7. ¢., that, aS in rie. 29.—Mandible of the lobster, 
the Phyllopodous limb, the maxillz of the De-#omerus americanus: pal, palpus. 
capods have no jointed axis, the limb consisting of epipodal and endo- 
podal portions alone, the stem or axis being wanting. In the maxillipedes, 
where part of the endopodal region of the limbs becomes, as Lankester 
claims, two multiar- 
ticulate endites, the 
fifth and sixth; or, as 
in the thoracic leg, be- 
comes a Single seven- 
jointed endite, the 
homologies cannot 
with certainty be 
traced. The lobster’s 
thoracic leg consists 
of the jointed axis ie hs 
which "is the homo! 2) cuseimid (Bb cccoud maxila'er lobster tm. bac pcueanemea 
logue of perhaps the thus) ; exp, coxopodite. (This appendage, with its five endopodal lobes, 
ftth  endite of the approximates nearest to the Phyllopod limb.) 
Phyllopodous foot, and the complicated gills and gill-fan (scaphogna- 
thite) correspond to the gill and flabellum of the Phyllopodous leg or 
flabellum. 
Tn brief the maxille of the Decapoda most 
closely resemble the leg of Phyllopods. The 
maxillipedes, for example those of the third 
pair, are much more differentiated than the 
S 
Fie. 31.—C, first maxillipede of lobster. Fic. 32.—D, second maxillipede: ex, 
‘ exopodite; end, endopodite; flab, epipo- 
dite or flabellum, or scaptogathnite. 
limbs of the Phyllocarida or Phyllopoda. In the Decapoda the gill and 
flabellum are homologous with those of the groups just enumerated; 
*The resemblance to the second maxillz of the young lobster in its first stage when _ 
freshly hatched is still more striking. See Smith’s Eazly Stages of the American 
Lobster, Pl. XVI, fig. 4. 
