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[525] INVERTEBRATE ANIMALS OF VINEYARD SOUND, ETC. 231 
lation at the base, and three set at the tip. The antenniw have large 
well developed scales, furnished along the inner margin with long 
plumose hairs, but the flagellum is shorter than the scale, not divided 
into segments, and has three plumose sete at tip. The mandibles are 
unlike on the two sides; the inferior edges are armed with acute teeth, 
except at the posterior angle, where there is a small molar area; the palpi 
are very small, with the three segments just indicated. The exognathus 
in both pairs of maxille is composed of only one article, and is furnished 
with several set at tip. In the first maxillipeds the exognathus is an 
unarticulated@process, furnished with short plumose hairs on the outer 
side. The second maxillipeds have the principal branch cylindrical, 
not ilattened and appressed to the inner mouth organs as in the adult; 
the exognathus is short, and as yet searcely flabelliform ; and the epig- 
nathus is a simple process, with not even the rudiment of a branchia. 
The external maxillipeds are pediform, the endognathus as long as and 
much resembling the endopodi of the posterior legs, while the exog- 
nathus is like the exopodi of all the legs, being half as long as the en- 
dognathus, and the terminal portion furnished along the edges with long 
plumose hairs. The epignathus and the branchie are very rudimentary, 
represented by minute sack-like processes. The anterior cephalothoracie 
legs, (Fig. D,) which in the adult develop into the big claws, are exactly 
alike, and no longer than the external maxillipeds. The pediform branch 
is, however, somewhat stouter than in the other legs, and subcheliform. : 
The legs of the second and third pairs are similar to the first, but not 
as stout. The legs of the fourth and fifth pairs are still more slender, 
and styliform at the extremity, as in the adult. 
The exopodal branches of all the legs and of the external maxillipeds 
are quite similar, and differ very little in size. In life, while the animal is 
poised at rest in the water, they are carried horizontally, as represented in 
Figure B, or are curved up over the carapax, sometimes so as almost to 
cover it. The blood circulates rapidly in these appendages, and they 
undeubtedly serve, to a certain extent, as respiratory organs, as well as 
for locomotion. By careful examination, small processes were found 
representing the normal number of branchiz to each leg.* These rudi- 
mentary branchiz, however, differ somewhat in different specimens, 
being very small, and scarcely distinguishable, in what appear to be 
younger individuals, from the rudimentary epipodi, while in others, ap- 
parently older, they are further developed, being larger, more cellular in 
structure than the epipodi, and even showing an approach to ecrenulation 
in the margins, as shown in Figure D. 
The abdomen is slender, the second to the fifth segments each armed 
with a large dorsai spine, curved backward, and with the lateral angles 
* The number of branchiz, or branchial pyramids, in the American lobster is twenty 
on each side; asingle small one upon the second maxilliped, three well developed ones 
upon the external maxilliped, three upon the first cephalothoracic leg, four each upon 
the second, third, and fourth, and one upon the fifth. 
