404. GEOLOGICAL SURVEY OF THE TERRITORIES. 
Phyllopoda. 
Archicerebrum { Merostomata (Limulus). 
The syncerebrum of the Tetradecapoda (Amphipoda and Isopoda), 
judging by Leydig’s figures! and our own observations (from dissections 
made by Mr. J. S. Kingsley) on that of Idotza and Serolis’, is built on 
a different plan from that of the Decapoda. The syncerebrum of the 
Phyllocarida is somewhat like that of the Cladocera and Copepoda (Cal- 
anid); being essentially different from that of the majority of the 
Malacostracous Crustacea. 
The Copepodous syncerebrum is an unstable, highly variable organ, 
but on the whole belongs to a different category from the syncerebrum 
of other Neocarida. 
We have then, probably, three types of syncerebra and two types of 
archicerebra among existing Crustacea. 
~ 
HOMOLOGIES OF THE CRUSTACEAN LIMB. 
Comparison with limbs of Cladocera.—We should naturally first com- 
pare the appendages of the Phyllopods with the members of their own 
ens 
en 1-3 
Fic. 27.—First leg of male of Moina (for comparison with that of male Limnetis): ez, exite; epip, 
epipodal portion of limb; en*—-en®, endites 4-6, to compare with the endites forming the hand of the 
male Limnetis. The base of the endopodal region (en 1-3) not differentiated as in the Phyllopod limb. 
order, and especially the Cladocera; and here, whether we consider the 
carapace-valves, the eyes single and compound, the two pairs of antenne, 
or the telson, we find a very close connection in form between Limnetis 
and Daphnia or Moina. In the accompanying figure from Grube’s 
and Weismann’s excellent paper on the Daphnide? (which we have 
slightly modified, introducing dots in the branchial portion) may be 
seen how nearly the first leg of the male of Moina rectirostris agrees 
with that of the male Limnetis, as seen in the sixth endite forming 
a claw like that of Limnetis, although the flabellum is not clearly dif- 
''Tafeln zur Vergleichenden Anatomie. Von F. Leydig. Tiibingen, 1864. 
2 Zoology for High Schools and Colleges, figs. 255, 256. 
3 Ueber einiger neue oder unvollkommen gekannte Daphniden. 1877. 
