176 Transactions.— Zoology. 
basal one broader and longer than the terminal one. The ends of both 
branches supplied with numerous rather long sete. Telson squamiform, 
sides arched, ending in a blunt point tipped with a few short sete. Colour 
transparent. Length of largest specimen -46 inch. 
Hab, Pump at Eyreton. ; 
As this Isopod is exceedingly interesting, I have endeavoured to describe 
and figure it in some detail. The mouth parts are all small and exceedingly 
difficult to make out, owing to the various parts being to a considerable 
extent anchylosed together; and I have to thank Professor Hutton for 
valuable aid in their dissection. Though I have by his aid succeeded in 
making out the various parts which form the mouth, I cannot, in the absence 
of sufficient books of reference, be quite certain of their homologies. All 
the parts of the mouth project forwards ; just below the antenne there is a 
strong moderately sharp labrum or upper lip (pl. X., fig. 8). The appendage 
which, by its position, should correspond to the mandibles does not appear 
to perform the function of mandibles. The two parts, right and left, appear 
to be here anchylosed together, and no trace of any palp is to be seen; the 
distal ends are fringed with very short indistinct sete, and the opposite end 
is notched (fig. 4). The first maxilla is simple, spoon-shaped at the end, 
which is fringed with sete (fig. 5). The second maxilla is also simple, 
straight, and towards the end it is supplied with short teeth (fig. 6). Though 
this appendage, by its position, appears to correspond to the second maxilla, 
yet it is the only one that looks at all like a masticatory organ. If the right 
and left halves were rubbed longitudinally together they would, owing to the 
short teeth at their ends, form a most efficient triturating organ. The most 
posterior of the mouth organs, the maxillipedes (fig 7), are somewhat concave 
and operculiform, enclosing the rest of the mouth parts. The basal parts of 
the two halves on the two sides are anchylosed together, and to the head 
itself, but the terminal portions are free, and the ends, which are at some 
distance apart, are tipped with sete. On each side, near the middle, is # 
peculiar looking small round piece, which is articulated to the rest of the 
limb. This may possibly represent a rudimentary exopodite, while the free 
terminal portion may be the endopodite of the typical Crustacean limb. 
The appendages of the abdomen on each side consist of a short basal 
joint supporting two more or less oval branchial plates (fig. 12). In the 
appendages of the first abdominal segment the outer branch is much 
enlarged and forms an operculum over the branchial plates; the inne? 
branch, which lies under the operculum, is narrow (fig. 11). In the view of 
the abdomen from below (fig. 10), the two halves of the operculum hav? 
been slightly separated from one another to show the branchial plates 
underneath. - 
