MARINE ISOPODA OF NEW ENGLAND, ETC. 327 



ments progressively decrease in length and width, and the seventh is 

 somewhat concealed at the sides by the swollen base of the pleon. The 

 basal segments of all the legs are much alike in form, and differ but lit- 

 tle in size throughout. They are cylindrical or slightly clavate, the first 

 pair perceptibly shorter and smaller than the second, from which they 

 increase very slightly to the sixth, which is the largest, the seventh not 

 being larger than the second. The legs disarticulate easily at the end 

 of the basal segment, and in the specimens examined nearly all are 

 broken off at this point. Beyond the basal segment the first pair are 

 comparatively short, about half the length of the body. The ischium 

 of the first pair is robust, and a little longer than the merus; the carpus 

 is subtriangular and armed with strong short spines on its palmar 

 margin ; the propodus is about as long as the ischium, slightly swollen, 

 and armed with a few spines ; the dactylus is short and armed at the 

 end with two stout curved claws, of which the outer is about twice the 

 length of the inner ; between the claws is a slender bristle. The sec- 

 ond and following pairs of legs are much more elongated than the first 

 pair, the elongation being principally in the carpus and propodus, and, 

 in a less degree, in the ischium and merus, while the dactylus is compar- 

 atively but little elongated. In the second pair of legs the propodus is 

 not longer than the carpus, but it becomes proportionally, as well as ab- 

 solutely, longer in the following pairs until, in the sixth pair, it may be 

 nearly or quite as long as the body and form about two-fifths the whole 

 length of the leg. The dactyli are, in all the legs, comparatively short, often 

 less than one-tenth the length of the propodus, and armed with two unequal 

 claws, of which the longer is about two-thirds as long as the dactylus 

 itself, and the shorter is more than half the length of the longer. In all 

 the legs the ischium is armed with a few short curved spinules, and the 

 elongated propodal segments are furnished with scattered, slender and 

 elongated, straight spines, each with a minute bristle near the apex. 



The pleon is remarkably swollen near the base, and is somewhat 

 pear-shaped ; posteriorly it is deep, and bears the uniarticulate uropods 

 in shallow grooves near the end. On the upper surface are a few 

 straight slender spines, and below it is covered in the females by an 

 ovate, obtusely-pointed opercular plate, and in the males by a trifid 

 operculum, the median portion being slender, with nearly parallel 

 sides and a central suture, and the two lateral portions slender, semi- 

 ovate and pointed behind. The pleon appears to be carried habitually, 

 during life, flexed upward at a considerable angle. 



The length of the specimen figured, by Mr. Emerton (pi. Ill, fig. 14), 

 is 1.2 mm , breadth 0.7 mm ; but specimens obtained in 1878 measure 3.1 mm 

 in length, 1.5 mm in width, in the female, and l.l 111 in the male. The 

 pleon measures in length l.l mm and in width O.S mm in the larger indi- 

 viduals. 



A single much mutilated specimen of this species was dredged in 12 

 fathoms, South Bay, Eastport!, in 1872, by the United States Fish Com- 



