THOMPSON : A HARE THALASSINID. 
17 
cially those on the pereiopod segments, and “ calcified bars ” are 
absent from their bases. Only males have been collected, and 
these bear pleopods on the second to the sixth abdominal segments. 
The rami of these pleopods are less acutely pointed than those of 
Naushonia’s pleopods. Heller clearly figures these appendages 
without a stylamblys (pi. 3, fig. 50), so that Cano’s assertion that 
this appendix is present has little weight. The uropods have 
broad-oval rami and the transverse suture on both is Hexed. The 
surface of the outer ramus is traversed by one, the inner by two 
longitudinal keels. 
As already noted, the posterior mouth parts are of the same type 
in both genera, Calliaxis showing those peculiar modifications of the 
maxillae (pi. 3, figs. 44, 4G) and maxillipeds (pi. 3, fig. 47-49) 
which are distinctive of Naushonia. The relative proportions of the 
parts of each appendage are also quite similar, with the following 
exceptions : the first maxillae have a more acute internal lacinia and 
a shorter palpus than in Naushonia ; the second maxillae have those 
divisions of the external and internal laciniae which are adjacent to 
one another, narrower than the outer divisions of these laciniae, 
while in the American genus all the divisions are more nearly sub¬ 
equal ; the scapliognathite is narrower; the expansion of the 
“endopod” in the first maxilliped is spatulate rather than triangular 
and the flagellum of the exopod is shorter; the flagellum in the 
exopod of the second maxilliped is not as long as the peduncle ; and 
in the third maxilliped the area of stiff bristles on the fourth joint 
is replaced by a serrate keel. Heller and Cano do not agree as to 
the length of the peduncle of the exopod in the second maxilliped, 
the former figuring it as equaling the endopod, the latter as only 
reaching the middle of its fourth joint. 
The first peduncular joint of Calliaxis’ antennula is short and the 
third elongate, while in Naushonia these joints are “long” and 
“moderate” respectively. The antennae have an elongate peduncle 
which exceeds the flagellum of the antennulae ; the first, second, 
third, and fifth joints are short, the fourth is elongate. The first 
joint bears three teeth on its distal border, the second has a blunt 
external spine. The flagellum is long and slender and the scale is 
reduced to a “ flat, three-cornered spur (stachel).” 1 
1 Cano asserts that this is absent, but his description and figures seem 
unreliable. 
