278 



through the just-mentioned superficial pore-chambers. They are covered by 

 strongly arched, pentagonally rounded kenozooecia, which are twice the length 

 of the gonozooecia, terminate at the top in a point and meet in parallel sutural 

 lines. Besides a circle of marginal pores, which are partially covered by neigh- 

 bouring zooecia, there are still a few scattered pores in their distal part. The well- 

 chitinized operculum (fig. 7 f), which has the form of a segment of a circle, has in 

 its proximal margin two small, rounded sinuses corresponding to two rounded pro- 

 jections on the proximal margin of the aperture. A little inside each lateral margin 

 we find a rounded process for muscular attachment. 



The colonies occur as circular or fan-shaped discs on algse, and, contrary to 

 all the other species of this genus that I have examined, the zooecia are arranged 

 in continuous, arch-shaped transverse rows. 



Two colonies of this species, without statement of locality, are found in the 

 herbarium of algse in the Botanical Museum. 



H. cornuta BuskS var. holostoma n. 

 (PI. XXI, figs. 8 a-8 g). 



The zooecia are elongated, generally pear-shaped, evenly ascending towards 

 the distal end and provided proximally to the aperture with a large strongly pro- 

 jecting, hollow expansion (fig. 8 g) bent more or less distinctlj' in the shape of 

 a knee, in which we may distinguish between a broader proximal part and a 

 narrower, at the end broadly rounded distal part. The aperture is wholly or 

 partly hidden by the latter part, when the colony is regarded from the frontal 

 surface. On the boundary between the two above parts the expansion mentioned 

 has an internal, transverse septum, which is perforated by a transversely oval 

 pore. As in the foregoing species we find ^n either side of the aperture a horn- 

 like expansion rounded at the end, which is however longer and more slender, 

 less bent towards the aperture, but directed more distally. A smaller expansion 

 is not infrequently found in the middle of the frontal surface, sometimes in the 

 central line, sometimes towards one lateral margin. The basal surface of the 

 zooecium, which has a small uncalcified portion centrally, is on its inner surface, 

 especially in its proximal half, provided with numerous, narrow, scattered, papilla- 

 shaped processes, which have the free end turned towards the distal end. Con- 

 trary to the other species examined by me the aperture (fig. 8 c) has no sinus, 

 and the bicusped hinge-teeth separate an almost semi-elliptic anter from a poster, 

 the height of which is only about one-third of the former and its slightly 



' 2, p. 84. 



