ON THE STRUCTURE OF CERATELLA FUSCA (gRAY). 21 



{4.) Ccratclla spiiiosa. (Carter.) 



Colony procumbent; thickly branched hard flexible ol' a dark rich red-jiurple colour. 

 Main branches round, brownish, covered with small, smooth, often suljspatulate erect 

 spines. Stem dividing subdichotomously into purple branchlets, which terminate in 

 abruptly pointed extremities. Hydrophores the same as in the foregoing species; 

 most prominent in the round branchlets to which they give, ai profil, a serrate 

 somewhat sertularian appearance, the teeth of which are inclined forward. Minute 

 stntcturc : Main stems composed of clathrate chitinous fibre, of which the meshes are 

 more or less oblong, passing into prominent longitudinal lines on the branchlets 

 where they terminate on the backs of the semitubular plates which respectively form 

 the floors of the hydrophores, to which they thus give support. Size of specimen, 

 which is merely a branch 4 J inches long by 2 broad. 



Locality. — Port Natal. 



Mr. Carter adds that "the spines on the surface distinguish this from the 

 foregoing species, add to which its longer and more pointed branches, longitudinally 

 ridged clathrate fibre and lich red-purple colour." 



Genus. Chitina. (Carter.) 



Colony erect, bushy, fragili flexible, fawn coloured. Trunk long, hard, 

 irregularly round, composed of many stems united clathrately and obliquely into a 

 cord-like bundle, which divides and subdivides irregularly into branches which again 

 unite with each other in substance (anastomose) w^ien in contact and finally form a 

 straggling bushy head. Hydrophores long clathrate tubular, terminating the ends 

 of the branchlets, or prolonged from some of the proliferous tubercles which beset 

 the surface of the trunk and larger stems. Minute structure : Composed of clathrate 

 chitinous fibre throughout, whose network is subrectangular and massive in the stems, 

 where there is no difference between the centre and circumference, with the exception 

 that the fibre is stouter in the former or oldest part; hydrophores composed of several 

 longitudinal fibres or ridges lattice-worked together transversely into a tubular form, 

 somewhat contracted at the extremity, in the centre of which is an aperture of the 

 meshwork a little larger than the rest. Height of specimens about 14 inches, trunk 

 about 1 inch in diameter; hydrophores averaging l-3rd of an inch long In- 

 l-60th of an inch in its broadest part and an aperture l-90th of an inch in 

 diameter. 



(5) Chitina ericopsis. (Carter.) 



The description of the species is the same as that of the genus. 

 Locality. — New Zealand. 



