84 THE VOYAGE OF H.M.S. CHALLENGER. 



fibrous bands, and (3) tlio lophioliexasters which lie near the outer surface, but yet 

 underneath the dagger-like hypogastralia. This form perhaps belongs to the genus 

 Holascus. 



Genus 2. Regadrella, 0. Schmidt. 

 1880. 0. Sclimidt, Die Spongien des Meerbusens von Mexiko, p. 6L 



Regadrella i^hcenix, 0. Schmidt (PI. XIII. figs. 1-4). 



Although Regadrella phoenix, which has been described by Oscar Schmidt, is in 

 general characters closely allied to the genus Eiq^lecteUa, remarkable differences occur 

 which may well suffice for the establishment of the genus. We have here, as in the 

 Euplectella, to deal with a tube whose walls are much perforated by round apertures, 

 and whose transversely truncated superior extremity is covered by a watch-glass-shaped 

 arched sieve-plate, and bordered by a cuff-like wreath of spicules. The basal tuft is 

 entirely absent, and the skeletal framework consists not of longitudinal and transverse, 

 but of oblicjue, irregularly interwoven strands of fibres, while the rosettes scattered in the 

 parenchyma are essentially distinct from those of the various species of Euplectella. 

 The inferior extremity of the tube has become converted into a compact and substantial 

 cup by extensive fusion of the spicules. The cup is fixed by a knobby base on the 

 stony substratum, while towards the upper end it passes quite gradually into a 

 progressively looser spicular framework. After the death of the sponge the part of the 

 skeleton which is not united by siliceous matter becomes separated from the rest of the 

 body, but the basal part persists, and so admits of the occurrence observed by 0. Schmidt, 

 that several generations encapsule one within the other, the younger forms settfing within 

 the remnants of their predecessors. 



Without entering upon a detailed description of all the individual forms of spicules, I 

 win confine myself to noting the differences between some Regadrella spicules and the 

 corresponding spicules of the genus Euplectella. 



The spicules which project freely from the undulating curved margins of the terminal 

 sieve-plate are hexacts, whose prolonged free distal ray is equipj^ed with scaly or prong- 

 like protuberances (PL XIII. fig. 2). 



AU the rosettes which are abundantly scattered in the parenchyma are distinguished 

 from the corresponding rosettes of Euplectella by the fact that their slightly bent 

 terminal rays, three or four of which S23ring from every short principal ray, do not run 

 out to simple points, but become divided at their narrowed extremities into four 

 transversely directed and cruciately disposed, hook-like, backwardly bent, fine prickles. 

 These forms should thus be designated not oxyhexasters, but rather discohexasters. 

 With regard to fig. 3 on PI. XIII., which represents a rosette of this kind from Regadrella 



