3i6 DISCOVERY REPORTS 



Genus Stelodoryx, Topsent. 

 Genotype. S. procera, Topsent, 1904, p. 174. 



Remarks. The original diagnosis reserves this genus for stipitate " Dendoricinae " 

 with skeleton composed of longitudinal branching fibres, continuous with the axial 

 skeleton of the pedicel, connected at intervals by single spicules placed at right angles to 

 the main fibres. Whether the disposition of the fibres in the genotype constitutes a sound 

 generic character is an open question. Perhaps the more distinctive feature of its 

 spiculation is, however, the presence of polydentate isochelae, and while it is doubtful 

 whether this constitutes a sufficiently good character for generic distinction, a distinc- 

 tion based on this character alone is as good as that at present maintained between 

 Myxilla and Lissodendoryx, genera closely allied to Stelodoryx. For the present, 

 therefore, I propose to adopt the genus Stelodoryx as a convenient arbitrary division of 

 those Myxilleae in which the distinctive feature is the presence of polydentate isochelae. 



Other species which fall naturally into Stelodoryx, as now understood, are Dendoryx 

 dentata, Topsent {loc. cit., p. 172), Myxilla diversiancorata, Lundbeck (1905, p. 150), 

 M. pluridentata, Lundbeck {loc. cit., p. 154), and S, discoveryi, sp.n. 



Stelodoryx pluridentata (Lundbeck). 



Myxilla pluridentata, Lundbeck, 1905, p. 150, pi. v, fig. 3, pi. xv, fig. za-i. 

 Occurrence. St. WS 243 : Falkland Islands, 144-141 m. 



Remarks. Except that the spicules are slightly smaller it is impossible to find any 

 difli'erence between the present specimen and the type of Myxilla phiridentata. The 

 chelae, for example, seldom exceed 0-065 ^'n^- chord, as against o-oyi-o-ogy mm., the 

 tornota vary from 0-24 to 0-28 mm., as against o-226-o-32 mm., although the ends show 

 the same variability in each case, and the styli, although much the same size, are some- 

 times slightly tylote in the present specimen. Externally, the two specimens agree 

 closely except that the type is much smaller, the present specimen measuring 4 cm. by 

 4 cm. by 5 cm. high. 



The specimen from Falkland Islands may be conspecific with the Arctic specimen 

 (i.e. the type), or the two may represent convergent species which are indistinguish- 

 able. At all events, the wide geographical separation is a point of interest. 



Distribution. Iceland. 



Stelodoryx discoveryi, sp.n. (Fig. 28). 

 Holotype. B.M. 28. 2. 15. 426. 

 Occurrence. St. WS 88: Falkland Islands, 96-127 m.; St. WS 90: Falkland Islands, 82-81 m. 



Diagnosis. Sponge irregularly massive ; surface even and smooth to the naked eye, 

 very minutely hispid when viewed with a hand lens; oscules 1-2 mm. in diameter, 



