137 



to the distal edge of the zooecium a large, semi-circular opercular valve is found. 

 The basal horizontal part of the distal wall has a large, somewhat curved trans- 

 verse group of up to 70 uniporous rosette-plates. On the boundary between 

 the horizontal and the obliquely ascending part of the distal wall two narrow, 

 tubular cavities issue (figs. 10 b, 10 d), which from each zooecium sink down into 

 the subjacent one. They are bounded outwardly by the lateral wall of the zooe- 

 cium and inwardly by a continuation of the distal wall, and in a transverse 

 section proximally to the latter they are seen as two small, round holes (fig. 10 c). 

 They touch the basal edge of the rosette-plate of the lateral wall and generally 

 end just proximally to it (fig. 10 d). On the basal side of the colony the edge 

 of the distal wall shows a number (6 — 10) of small, distally pointing, short, 

 broader or narrower, sometimes bifurcate crenulations (figs. 10 b, 10 c), which 

 are really outpushings from the lower into the higher placed zooecium, and 

 alternating with them is seen a number of much more faint ones pointing 

 proximally. 



The avicularia, only occurring on the outer lateral margin of the marginal 

 zoa'cia, are very large, turned towards the frontal surface of the colony and 

 furnished with a well-developed beak and mandible hook. A great part of the 

 avicularian cliamber is enclosed in the zooecium, and its strongly arched endozocecial 

 surface lias about 10 scattered, uniporous rosette-plates (fig. 10 e). The marginal 

 zooecia have an obliquely triangular transverse section, ending outwards in a 

 rounded edge, and (he outer of the two above-mentioned, narrow lateral cavities 

 passes obliquely across the basal side of the avicularium, being only visible 

 from the basal surface of the colony. On the basal side the zooecium is separated 

 from (he free part of the avicularium by the just mentioned cavity, and on the 

 frontal side by its upper lateral margin, which runs obliquely outwards to a 

 small indentation in the approximate centre of the lateral margin of the avicu- 

 larium. A corner is formed here corresponding with that of the other zoa'cia. 

 In the outer half of a marginal zocrcium we may distinguish between a frontal 

 and a basal, distal lateral margin, which together enclose the avicularium and 

 mark the boundary between the free part of the latter and the part immersed 

 in the zoa'cium. On Ihe other hand there is but a single proximal lateral margin, 

 as the frontal and the basal lateral margins are here run together in an edge. 

 Instead of the calcified lateral wall in the other zoa-cia we thus find here but a 

 strongly calcified rib, which however generally shows a distinct separation into 

 two lateral halves, enclosing between them a rosette-plate (fig. 10 e). 



No ooecia. 



The colonies are unjointed, single-layered, dicholomously branched with 



