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438 PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM.’ 
carapax is considerably more slender than in P. Montagui, and the pos- 
terior tooth of the dorsal carina is farther forward, being much in front 
of the middle. The abdomen is more slender than in P. Montagu; but, 
except for the greater slenderness, there is scarcely any difference in 
the form or proportions of the somites, or the form and armature of the 
telson and uropods. There are slender exopods, about a third as long 
as the ischia, at the bases of the external maxillipeds, but the endopods 
themselves are as in P. Montagui; the merus reaches to the base of the 
flagellum of the antenna, and the tip falls considerably short of the tip 
of the antennal scale. | 
The first pair of legs are nearly as in P. Montagu. The right chelate 
leg of the second pair is shorter and stouter than in P. Montagui, and 
scarcely reaches the tip of the corresponding leg of the first pair; the 
ischium is about a fourth the entire length; the merus is only a little 
shorter than the ischium; the carpus increases in thickness distally, is 
a little longer than the ischium, not more than about once and a half as 
long as the merus, and usually composed of only five segments, the 
proximal half being wholly unsegmented or annulated, then three sub- 
equal and very distinct segments, about as broad as long, and these fol- 
lowed by the terminal segment, which is about as long as the three next 
preceding; the chela is about half as long as the carpus and a little 
stouter than its distal end.* The left chelate leg is a little shorter and 
stouter than in P. Montagu, but has about the same number of seg- 
ments in the merus and carpus, and does not differ in other respects. 
The third, fourth, and fifth pairs of legs differ from those of P. Montagui 
in being a little more slender and in having much longer, much more 
slender, and nearly cylindrical dactyli, which are wholly unarmed, except 
a few small spinules beneath near the base. 
*The proportions of the segments and the segmentation of the carpus in the un- 
equal second pair of legs in the genus Pandalus appear to be usually very constant and 
to afford very good specific characters, but they occasionally present very remarkable 
variations. In carefully examining several hundred specimens of this species, only 
about half a dozen were found which varied from the above description in the seg- 
mentation of the left carpus; two or three specimens had an additional but less dis- 
tinctly indicated segment back of the four distal ones, making six in all. Two speci- 
mens had three additional segments inserted in the same way, making eight in all; 
but in both these specimens the segmentation was more or less irregular, and the addi- 
tional segments may have resulted from some injury. One large female, quite normal 
in other respects, has the right carpus multiarticulate throughout and composed of 
about eighteen segments, nearly as in P. Montagui; the whole leg, however, is shorter 
than in other specimens of the same size, and may have been reproduced, though I 
cannot see how this would explain its abnormal structure. Detailed measurements 
of both chelate legs in most of these abnormal specimens are given beyond in the tables 
of measurements. 
One female, 70™™ long, stations 290 to 291, 30 to 31 fathoms, off Cape Cod, has the 
chelate legs reversed, just as in the specimen of P. propinquus already referred to. 
