108 
8. I. Smith — Crustaceans of the Atlantic Coast. 
the anterior part of the carapax a little smoother than usual in the 
species, but the difference is very slight and apparently not constant, 
and it may be due to the bad state of preservation of the specimens. 
The specimens from off Halifax, and most of those from the Gulf of 
St. Lawrence, agree perfectly with the European specimens which I 
have examined. 
Diastylis politus, sp. nov. 
Adult female. — The cephalothorax is elongated and, including the 
lateral spiuiform processes of the last segment, nearly half as long as 
the length from the tip of the rostrum to the tip of the telson, pretty 
regularly oval in outline as seen from above, and regularly and 
strongly convex dorsal ly as seen from the side. The carapax is rather 
more than half as long as the whole cephalothorax, about three- 
fourths as broad as long, and very much longer than high. The 
posterior edge is regularly arcuate and has an elevated margin which 
extends round the broadly sinuous inferior edge to an angular prom- 
inence below the base of the rostrum as in T). sculptus , and the ante- 
rior portion of the inferior edge is minutely dentate as in that species. 
The rostrum is short, nearly horizontal, and rather obtuse as seen 
from above. 
The surface of the carapax is naked and nearly smooth, except that 
the anterior portion is areolated somewhat after the manner of D. 
sculptus , but the areolations are fewer and less deeply excavated, and 
they do not extend to the postero-lateral portions of the carapax as 
in that species. As seen from above, there are two minutely dentate 
transverse crests, as in D. sculptus, upon the semi-circular median 
lobe, and the posterior of these extends across the lobe and connects 
with a perpendicular crest which extends in a nearly straight line to 
the lateral margin just back of the angular prominence below the 
base of the rostrum. In front of this vertical crest each side there is 
a short and prominent crest, slightly curved and nearly parallel with 
the inferior margin, but which does not reach the inferior margin of 
the rostrum and fades out posteriorly before it reaches the vertical 
crest. Just back of the first vertical crest, is a second which curves 
sharply forward and connects with the first below, but which is 
straight and slightly diverges from the first above. At the suture 
round the median lobe this second crest is connected with the first 
by a short ridge, so as to leave a nearly square area, as in D. sculptus , 
each side of the median line, as seen from above, and just back of the 
posterior transverse crest of the median lobe. Just back of the upper 
