A*^. / Smith — Cnistacearis of the Atlantic Coast. 99 



Pseudomma truncatum, sp. nov. 



Plate XII, figures 3, 4. 



This species is neai-ly 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 diflerence in 

 the sexes in the form of the anterior margin. The antennulse 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 

 antennje 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 regulai'ly arcuate and furnished with in the neighborhood of thii'tj' 

 setje; the terminal portion, in fj-ont 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 setje until near the tip where there are three to five more, closely 

 crowded together as on the inner margin. In P. roseum the terminal 

 poi'tion 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^ 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 the 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 

 of the same sex and size, and even on the diff"erent sides of the same 



