279 



converging lateral margins meet in an almost straight or slightly curved 

 margin. The well-chitinized operculum has on the other hand a broadly quad- 

 rangular, accessorial (fig. 8 d) and within each lateral margin a short, slightly 

 curved muscular ridge. As in the preceding species we find two large distal pore- 

 chambers bounded by the angularly bent distal wall, while each lateral wall has 

 3 — 4 communications with the neighbouring zooecia. 



The ooecia (figs. 8 b, 8 c) occur in small numbers scattered among the zooe- 

 cia, and the gonozocecia are provided with a large, broad, somewhat flat^ lip- 

 shaped, obliquely ascending expansion which is situated proximally to the aper- 

 ture. The latter is wholly or partly hidden by the expansion and its proximal 

 margin is slightly angularly bent. The operculum (fig. 8 f) has a small, com- 

 pressed process on either side. The strongly arched kenozooecia have a number 

 of scattered pores, which are however wanting in the steeply ascending portion 

 distally to the aperture and the projecting central portion of the frontal surface 

 is generally developed as an expansion, more or less sharply delimited. 



As the form just-described differs in the want of a sinus in the poster of the 

 aperture from Lepralia hgalina, var. cornuta described and figured by Busk^ 

 I originally felt inclined to consider them specifically different in spite of 

 the corresponding development of expansions. But as I have had a later op- 

 portunity of examining an apparently closely related form from Victoria, the 

 aperture of which is provided with a well-developed sinus (fig. 9 b), I must 

 suppose all three forms to be varieties of one species, Hippothoa cornuta Busk, 

 which is very variable, not least in the form of aperture. This variety may 

 be termed aporosa. The three expansions are of a similar form and structure 

 as in var. holostoma, and the median expansion especially is provided (fig. 9 a) 

 with a similar septum perforated by a pore. The gonozocecium (fig. 9 c) has a 

 similar lip-shaped expansion, but its aperture, like the zooecial aperture, is pro- 

 vided with a narrow, deep sinus, to which a process on the operculum (fig. 9 e) 

 corresponds. The kenozocecium, which to judge from the figure only possesses a 

 circle of marginal pores in Busk's form, is here at the outside furnished with a 

 few median pores and is even more strongly arched than in var. holostoma, its 

 surface being very hunched. A small colony from Victoria has been found on 

 Pterocladia lucida in the herbarium of algse in the Botanical Museum. 



' 2, p. 84, PI. XCV, figs. 3—5. 



