146 TANAIDA. 
Dr. Fritz Miiller (Archiv. f. Naturg. Jahrg. 1 Bd. p. 1) 
and Van Beneden (Ueber der Bau der Scheerenasseln 
Assellotes Heteropodes M. Edw.) to attribute it to the 
Macrourous Decapods, each basing his opinion, arrived at 
independently, upon the supposition that the union 
of the head with the first joint of the body is an 
incipient effort in the development of a carapace—the 
latter author, moreover, asserting that respiration is 
carried on beneath the carapace, although he states that 
he has not been able to detect any especial organ adapted 
to that purpose. 
From this view of the question we must entirely dissent, 
first, because the branchial organs in decapod crustacea 
are essentially appendages of the coxe or first joints of 
the limbs attached to the pereion or pleon: consequently, 
all these limbs being posterior to the cephalon, the 
organs of respiration cannot be developed beneath it; 
second, because the carapace is not developed by a fusion 
of the segments of the pereion with those of the ce- 
phalon, but by a monstrous production of the integu- 
ment of the latter extending back, over, and covering 
the segments of the former; and so, in the typical 
decapoda, overlying and protecting the segments of the 
pereion, and consequently the branchial organs also. 
This genus also approaches towards the Podophthalmous 
crustacea, and more particularly the Macrourous order, in 
the form of the eyes and inferior antennz, whilst it re- 
sembles the Amphipoda in the character of the legs and 
the general slenderness of the body. It also approaches 
the Squille in the character of the pleopoda, and the 
Isopoda in that of the posterior pair of pleopoda. 
One interesting and, as far as we know, unique feature 
in these crustacea yet remains to be noticed. The segments 
of the pleon have the lateral walls (long known as the 
