278 



tlirough Ihe jiist-mentioncd superficial poie-cliambers. They arc covered by 

 strongly arched, peiitagonally rounded kenozocrcia, which are twice the length 

 of the gonozorecia, terminate at the lop in a \unni and meet in i)arallel sutural 

 lines. Besides a circle of marginal jiores, which are j)arlially covered by neigh- 

 bouring /oa-cia, there are slill 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 alg:v, and, contrary' to 

 all the other species of this genus that I liave examined, tlie zotrcia are arranged 

 in continuous, arch-shaped transverse rows. 



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

 lierbaiium of alga- in the Botanical Museum. 



H. cornuta Busli', var. holostoma n. 

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



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. <S g) bent more or less distinctly in the shape of 

 a knee, in which we may distinguish Ix'twcen a broader proximal j)art and a 

 narrower, at the end broadlj' 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 on either side of the aperture a horn- 

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

 less bent towards the aj)erture, 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 ba.sal surface of the 

 zoa-cium, which has a small uncalcified portion centrally, is on its inner surface, 

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

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

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

 and the bicusped binge-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. 



