271 



hearing zociecia. In the former it springs from the lateral surface of the zoa'cinm 

 close to tlie zigzag ridge and at a fairly great distance from the distal wall, and 

 in the latter it starts from the approximate centre of the proximal part of the 

 frontal surface. In both cases it ends in the above-mentioned, collar-shaped i)art 

 at the base of the oa^cium. To keep the covering-membrane extended there is 

 further a very small, flat, most often trapeziform process situated on each side 

 of the aperture. This process Busk wrongly takes to be an avicularium (hgs. 

 1 a, 1 f). 



Along the frontal margin of the abramal zigzag ridge we find on each zooe- 

 cium a longitudinal row of 5 — 7 small, widely separated, uni[)orous rosette-plates, 

 and similar rosefle-plates appear on both sides of the adramal arch-shaped ridges. 

 Along the frontal margin of the ridge there are 6 — 8, while those on the other 

 side of the ridge are more varying in number (^ — 7), and may sometimes be 

 rather irregularly scattered. Finally each of the two frontal rows of rosette-plates 

 is continued into a row or grou[) of 4 — 8 plates situated on each side of the 

 aperture. 



The obliquely a.scending distal wall has a basal trilobed margin and is pro- 

 vided with numerous, uniporous rosette-plates, which are scattered over its entire 

 surface, and such plates appear also in a longitudinal belt or row, which passes 

 Ihrough the whole centre of the basal surface (fig. 1 d). 



The obliquely truncated aperture, which forms an obtuse angle with the fron- 

 tal surface, has a semi-circular anter, while its poster is provided with a well- 

 developed rounded sinus. The slightly chitinizcd operculum, which is of a 

 corresponding forLu, has a somewhat curved, transverse row of round, bright 

 spots. 



The ooecia are of a most |)eculiar structure, being endozoa^cial and al the 

 same time having their endoocrcium situated frontallj' to the cry[)tocj'st of the 

 zod'cium, whicJi is much excavated to receive its strongly arched basal surface. 

 There is a transparent ectooa'cium, formed by the covering membrane, and a 

 calcilied, radiately striated endoooecium, which is somewhat nan-owed at the base 

 in the shape of a neck, and the form of which is that of a Phrygian cap rounded 

 at the end. A large |iart of the frontal surface of the endoocrcium is provided 

 with numerous, round, attenuated spots. The distal wall belonging to the ocecium 

 has rosette-plates not only in its basal trilobed pari but also in the narrow part 

 bounding the on'cium on either side. Finally, il may also be i-enuirked llial llie 

 oo'cium can be closed by the operculum of the zoo'cium. 



The colonies arc richly branched, bifurcated tufts with compressed branches 



