S. T. Smith — Crustaceans of the Atlantic Coast. 
09 
Pseudomma truncatum, sp. nov. 
Plate XII, figures 3, 4. 
This species is nearly allied to P. roseum and resembles it very 
closely in form and general appearance. The new species has pro- 
portionally shorter pereopods, however, and is readily distinguished 
by the terminal portion of the antennal scale and by the form of the 
telson. 
The form and proportions of the carapax and abdomen are exactly 
as in P. roseum. The ophthalmic segment (Plate XII, figure 3 a) is 
a little broader in front than in P. roseum , the dentated portions of 
the margin are slightly more lateral and the dentations not quite as 
well-marked as in that species, and there seems to be less difference in 
the sexes in the form of the anterior margin. The an ten nuke are as 
in P. roseum , except that the flagella are apparently a little shorter. 
The relative proportions of the segments of the peduncles of the 
antennae are the same as in P. roseum. The squamiform appendage 
(figure 3) of the antenna is about three and a half times as long as 
broad: the outer margin is about five-sixths of the entire length and 
terminates in a stout tooth, as in the allied species; the inner margin 
is regularly arcuate and furnished with in the neighborhood of thirty 
seta*; the terminal portion, in front of the base of the terminal spine 
of the outer margin, is regularly and rather broadly ovate and not 
longer than the breadth of the scale ; the setae of the outer portion 
of the terminal margin, from the base of the lateral spine to near the 
tip, are nearly or quite twice as remote from each other as on the 
corresponding part of the inner margin, there being only three or 
four seta* until near the tip where there are three to five more, closely 
crowded together as on the inner margin. In P. roseum the terminal 
portion of the antennal scale is proportionally longer than in P. trun- 
catum , being about one and a half times the breadth of the scale in 
advance of the base of the lateral spine, and the seta j on the outer 
portion of the terminal margin are as closely crowded as on the inner 
margin and twice or three times as numerous as in P. truncatum. 
The oral appendages are as in P. roseum. The second gnatho- 
pods (third maxillipeds) have the same structure and proportions of 
the distal and proximal segments of the endopod, and tin* same num- 
ber of segments in the flagelliform portion of the epipodal branches, 
as in P. roseum ; but the three longest segments (the meral and the 
divided carpal), though varying considerably in different individuals 
<>f | lie same sex and size, and even on the different sides of the same 
