248 AMERICAN PARASITIC COPEPODA. 
while the basal one bears two discoidal chitinous outgrowths, armed 
with curved points, of which one is lateral, while the other is 
ventral, in position (0 and o', Figs. 3 and 5). 
The mandibles (Fig. 6) are 0.1 mm. in length, of which one-third 
belongs to the toothed portion. This differs from any of the maud- 
ibles figured by Kurz in the absence of secondary teeth. 
The maxille (Fig. 7) are tri-articulate, the basal joint inflated on 
its lateral aspect, and the terminal joint ending in an outwardly- 
directed curved spine. The palp originates from the distal part of 
the second joint above a spine, and itself terminates in two sharp 
points. The maxille measure 0.095 mm. in length, of which one- 
half is occupied by the basal joints. 
The maxillipedes of the first pair, as in the other members of the 
genus, originate behind the second pair, and are independent as far as 
their attachment to the bulla. This is best described as mushroom- 
shaped, and its bilateral character is as well indicated by a surface 
view (after the fragments of gill have been removed from it), (Fig. 8), 
as by the fact that it is easy to prepare separately the halves be- 
longing to each maxillipede (Fig. 9). 
The maxillipedes of the second pair measure 0.73 mm. in length, 
and present the typical characters described by Kurz for these 
appendages in other Lernzopodide. Their specific characters may 
be studied in Figs. 3 and 10. 
Fig. Il reproduces the punctated appearance presented by the 
border of the lower lip, which measures 0.03 mm. from its attached 
to its free margin; the latter has only a very narrow fringe. 
On comparing Olsson’s figures of Z. alpinus with mine, it is appa- 
rent that the bulla presents considerable resemblance ; the 2nd 
antenne also bear a similar spiny excrescence, but have a pointed 
instead of a blunt ventral branch ; while two chitinous appendages 
project between the maxille from the ledge uniting their basal 
joints. If the figure of the 2nd maxillipede is accurate, it also 
differs considerably in outline. The details of Milne-Edward’s figure 
of Basanistes salmonea are insufficient for comparison, but the resem- 
blance of the 2nd antenne and the 2nd maxillipedes (3¢, 3a, Pl. XLI. 
loc. cit.) is sufficiently striking to justify the conclusion that the 
form found on the European S. wnbla and on our Brook Trout ara 
Loe, cit., Taf. V., Figs. 10, 11, 12, 13. 
