108 S. I. iSmU/i — Crustaceans of the Atlantic Coast. 



the anterior part of the carapax a little smoother tliaii 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 fe)nale. — The cephalothorax is elongated and, including the 

 lateral spiniform 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 dorsally 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 D. 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 areolatious 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. sculjytiis, 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 mai'gin 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 Avith 

 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 iirst 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. scidjytus, 

 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 



