266 '■ ENDEAVOUR " SCIENTIFIC RESULTS. 



Genus Selaginopsis, Allman. 



Selaginopsis dichotoma {Allman). 



Dictyocladium dichotomum, Allman, Rep. Sci. Results 

 " Challenger " Exped., Zool., xxiii., Hydro ida, pt. II., 

 1888, p. 77, pi. xxxvi., fig. 2, 2a. Id., Levinsen, 

 Vidensk. Medd. fra den naturh. Foren, 64, 1913, p. 277. 



Selaginopsis dichotoma, Billard, Ann. Sci. Nat., Zool., (9), 

 xi., 1910, p. 16, fig. 5. 



Hydrophyton monosiphonic, four or five inches in height, 

 in one plane, and forming a network by the anastomosing of 

 the numerous dichotomous divisions ; jointed usually at the 

 origin of the branches, rarely elsewhere. 



Hydrothecae spirally arranged, each fifth one completing 

 the spiral, so that there are four longitudinal series ; 

 tubular, stout, curved outwards, adnate most of their length, 

 or with one-third part free, very often continued outwards by 

 five or six renewals for a distance equal to fully half their 

 original length ; border very delicate, with three deep 

 emarginations and a three-valved operculum. 



Gonothecse large, ellipsoid, erect, springing from the inner 

 side of one of the branches just above a bifurcation, and 

 occupying the axil ; encircled by a very wide spiral wing, 

 the perisarc of which is double, with numerous internal radial 

 thickenings ; mouth a narrow tube, slightly expanded at the 

 end. 



The description and figure of this interesting species in the 

 " Challenger " Report are incorrect in a nvimber of particulars, 

 especially in regard to the form and arrangement of the 

 hydrothecae and gonothecse. Billard has already pointed out 

 some of these inaccuracies. 



All the subdivisions of a colony are in one plane, as shown 

 by Allman, and are united into a reticulum by frequent 

 anastomoses. The ramification is strictly dichotomous, the 

 two members of a bifurcation being about equal, and divergent 

 at a similar angle. A distinct constriction occurs at the origin 

 of one or both, and few other joints exist. The branches are 

 extended beyond the hydrothecate portion into twisted 

 tendrils, which terminate in attachment to the aperture of a 

 hydrotheca on another branch. 



With regard to the arrangement of the hydrothecae, Billard 

 justly remarks that Avhile they are, as Allman indicates, in 

 four rows, they are nearly equidistant, and not in groups of 

 four, as shown in Allman's figure. A series of five makes a 



