REPORT ON THE CB,TJSTACE4i MACRURA. 25 



hrobranchia the central or upporting axis, particularly towards the bj 

 appears to be rigid and multiarticulate, each articulus supporting one or more obtu 

 pointed processes, the rudini , robably of undeveloped trichobranchiate fila: □ 



The mastigobranchia, with adant podobranchial plume attached to the coxa of 



the first pair of pereiopoda, resembles that of the second pair of gnathopoda both in 

 and form. At its base are two fasciculi of Long lit hairs, which under the 



microscope are seen to be fringed with fine cilia. Those thatspring from the apex of the 

 mastigobranchia are, under the fifth of an inch microscopic pow< their ed 



serrated rather than ciliated. The anterior arthrobranchia i short, supporting on 

 the under side a row of moderately long trichobranchial filam m; th( 



upper li I of these at the base, while the distal extremity supports three broad 

 phyllobranchiate petals. The posterior arthrobranchia is lo d phyllobranchi 



the petals being arranged on the posterior margin of the stalk longitudinally from the 



■ to the apex. A bundle of pendent trichobranchiate filamente is attached to a rigid 

 and curved support that appi o I"- only connected with, and not part of, the 



longitudinal axi of the long phyllobranchiate plume. 



The ma nchia and podobranchia belonging to the second pair of pereiopoda 



bear a close resemblance to the appendages attached to the first pair. The anterior and 

 posterior arthrobranchia arc a 1. so similar, consisting of a long plume of phyllobranch 

 petals, one or two of which at the base arc double, beneath which j- a bundle of tricho- 

 branchiate filam< 



The mastigobranchia of the third pair of pereiopoda supports no podobranchial plume, 

 and the anterior and posterior arthrobranchiae are long and well developed, resembling 

 thoseof the second pair, being phyllobranchiate, and having the 1- t the base, 



near the »f which, on the under side, a bundle of trichobranchiate filamente 



attached. 



The mastigobranchia of the fourth pair of pereiopoda, like that of the preceding pair. 

 supports no branchial plume, and the arthrobranchiae also resemble the preceding, but are 

 much longer, and in the posterior the trichobranchial filaments extend to the fool of the 



:d petal, decreasing in length gradually from the base, where they arc abundant, to 

 the extremity, where they thin out to a single row. 



There is neither mastigobranchia] lash nor branchial plume attached to the fifth pair of 

 pereiopoda and the posterior somite of the pereion. Thi ed with 



of the pereion, but connected by membranous attachments, thai of a limited 



amount of movement on the part of the somite, and one of a more extended degree in 

 every direction in th of th • posterior pair of pereiopoda. 



The branchiae are of two distinct kinds, one eo j of finger-like pro© 



cylindrical filaments, the other of broad thin foliaccous plates. The former arc tricho- 

 branchise, the latter are phyllobranchiae. 



ILL. EXP. — PART LII. — 1- Fflf i 



