THOMPSON : A RARE THALASSINID. 
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bar (cb) which is free at the tip, is attached to the base of the masti- 
gobranchs of the pereiopodal segments, i. e ., k, /, m, and n. 
Maxillipeds. Pereiopods. 
g. h. i. k. 1. m. n. o. 
000 00000 Pleurobranchs. 
122 22220 Arthrobranchs. 
011 11100 Podobranchs. 
Ill 11110 Mastigobranchs. 
• Pleopods : first pair present in female, wanting in male ; unira- 
mous, slender, tapering ; one basal and several apical joints. Second 
to fifth pairs (pi. 1, fig. 19) biramous; rami lanceolate, subequal, 
hair-fringed, feebly calcified, without stvlamblys. Uropods (pi. 1, 
fig. 13) with transverse suture on both rami; rami broad-oval, sub¬ 
equal, suture serrate, straight in male specimen, on inner ramus in 
female bent where it crosses the slight keel; borders with external 
spine and fringe of long hairs. 
This genus clearly belongs in the Thalassinidea, but its position 
within that group is uncertain. The flat, prominent rostrum, well 
developed antennal scale, moderate abdominal epimera, and the large 
number of podo- and mastigobranchs recall the more primitive genera 
of the group, as do also the structure of the maxillae and the general 
form of the body. On the whole, its affinities, then, are rather with 
the Axiidae than with forms allied to Gebia or Callianassa. But in 
many anatomical details it differs widely from the members of this 
family and also, in a few cases, from all other Thalassinids. For 
example, the form of the carapace grooves and the phyllobrancliiate 
gill filaments suggest Callianassa. The first maxilliped resembles in 
its general plan the appendage as developed in Axius, Gebia, Cal¬ 
lianassa, and Thalassina (Boas, ’ 80 ), but the expansion of the 
endopod is unlike anything found in those genera. The second 
maxilliped in its general form is quite unlike the corresponding 
appendage of the above mentioned genera, especially in the elon¬ 
gate angle on the penultimate joint of the endopod. Naushonia 
is further distinguished by peculiar combinations of characters. 
Prominent among such are the gills, which are unusually numerous 
(eighteen), without pleurobranchs, with noticeable development of 
the mastigo- and podobranchs, and with phyllobrancliiate filaments ; 
