R. PHIEXIX. — GEN. CHARACTERS. 269 



with small irregularly papilla-like pro)m7iences, not more tlian 

 lY'i '"HI- i'l height. These are evidently caused by the hydranth, 

 invariably contained in tliem, of a commensal Hydrozoa which 

 is harbored in the sponge-wall. The prominences were not 

 observed in the uppermost region of the body only ; whether as 

 the result of abrasion or not, could not be determined. Under 

 the hand-lens, their summits as also the free edge of the cuff 

 appear to be spiny (PI. XI, fig. ?>). Tlie spines, protruding for 

 not more than half a millimeter, are found to be the distal rays 

 of certain specially developed dermal hexactins. 



Are the papilla> to be regarded as something of constant 

 occurrence in the species ? In consideration of what we know 

 about the relation of the WaUeria species to the commensal 

 Hydrozoa (see anon, under W. leuckarti), this question is possibly 

 to 1)6 answered iu the allirmative. However, nothing like the 

 papilhe, or the peculiarly modified dermalia (PI. X, figs.- 25-27) 

 in connectiou with them, h;is before been described from 

 R. pJuraix. 



The coarse parcnrkymal IxiikUcs, exposed on the external 

 surftice, pursue a, sinuous course in oblique or in nearlv longi- 

 tudinal directions (I'l. XI, fig. 2). 1'he bundles, more deeply 

 situated and exposed on the gastral surface, take a course which 

 is incliued to be transverse in direction, siuiilarly as we have 

 seen in other species of the genus. 



In the upper part the principal bundles of the skeleton run 

 obliquely right up to the sieve-plate border, exactly as is to be 

 seen in the figure of li. phanix given by .Sciiulze iu the C*hal- 

 lenger Report. 



Some bundles, but l>y no means all, extracted from the lower 



