422 
ZOOLOCxY OF THE FAR EAvST. 
two-jointed, outer margin of proximal joint with a few short setae, distal joint of 
peculiar shape the pointed apex of the distal protuberance studded with small spines, 
a pad of similar spinules on the inner proximal margin of the distal joint ; endopod 
without setae. 
None of the males which I dissected had an appendix masculina on the second 
pleopod but as none of my specimens measured more than () mm., they may not have 
been fully grown. I could not detect with certainty any definite branchial plications 
on any of the pleopod s. 
The general form of this species is shown on pi. XVI, fig. i. This figure agrees 
very closely with Thielemann's figure and my specimens agree with his description 
very closely except that pleopod four has fewer plumose setae on each ramus. 
As Thielemann points out this species differs from Hansen's description of the 
pleopods of the hemibrachiate Sphaeromids in having plumose setae on the fourth 
pleopods. Hansen says that the fourth and fifth pleopods are never furnished with 
such setae. 
I have examined six specimens of E. oregonensis^ Dana, sent me by the United 
States National Museum, from Sitka, Alaska, on the beach. Five of these are males 
measuring lo mm. and one a female measuring 8 mm. The pleopods agree substant- 
ially with those I have described above, the fourth pair has plumose setae on each 
ramus, more numerous than in my specimens but otherwise the same. The males 
also possess an appendix masculina, from which I have concluded that if my speci- 
mens belong to the same species, the males are still immature. 
All the males of these Alaskan specimens have a dense fringe of hairs on the 
fourth, fifth and sixth joints of the fourth and fifth pairs of thoracic limbs, but these 
hairs are not present in the single female. Hansen says that the thoracic limbs of 
the hemibranchiate vSphaeromids never exhibit .sexual differences. If the above 
specimens from Alaska have been correctly interpreted, E. oregonensis forms an 
exception to this general statement. None of the Chinese specimens exhibit these 
hairs, but they are otherwise so closely in agreement with the Alaskan specimens 
that I have regarded them as immature and not fully grown, the appendix 
masculina of the second pleopods in the male and the fringe of hairs on the fourth 
and fifth thoracic limbs being both characters denoting sexual maturity. 
If all the records ascribed to E. orcgeiiensis refer to the same species, it has 
a very wide distribution in the shallow waters of Eastern Asia from China to 
Kamtschatka and Western America from Alaska to California. It is also capable of 
living equally well in pure sea-water or in fresh water as in China or Japan and in 
Alaska as recorded by Richardson. 
It is possible that the specimens recorded by Thielemann from Japan and here 
from China are brackish water varieties of the type, characterised by their smaller 
size and the modification of their secondary sexual organs and it is also conceivable 
that the general appearance of the pleopods and the absence of definite plications 
in my specimens from China, may be correlated with the special habitat in which 
they were found. 
