146 TANAID^E. 



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 coxae 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 antennas, whilst it re- 

 sembles the Amphipoda in the character of the legs and 

 the general slenderness of the body. It also approaches 

 the Squilla 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 



