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calcified outer and a more slightly calcified inner (median) part. The distal wall 

 is acute-angled and the two arms are a little concave. As in the foregoing species, 

 it is at the same time saddle-shaped, and furnished with a transverse row of 

 (up to 12) uniporous rosette-plates. The distal half of each side-wall has ca. 6 

 rosette-plates. The marginal region, which consists of kenozooecia, only differs from 

 the marginal region in the preceding species by the part, which appears on the 

 basal side of the colony, being much calcified and furnished with similar stripes 

 to the zooecia. On the other hand, it has no distinct cryplocyst. The radical 

 fibres issue from the proximal corners of a number of fenestrse. 



Avicularia have not been found hitherto. 



The ooecia are high, dome-shaped, with indistinct radiating striae and gener- 

 ally in the middle provided with a shorter or longer, sometimes rather irregular 

 ridge. A low cryptocyst belt covers their proximal part. Also here the basal part 

 of the distal wall lies higher than the top of the ooecium and is thus seen dis- 

 tally to the latter at a deeper level (PI. I, fig. 6 b, PI. XXII, fig. 2 a). The distal 

 wall belonging to the ooecium forms an angular or sometimes almost arched 

 mark on the basal side of the colony, and the two arms are not concave but 

 convex. The ooecia-bearing zooecia are, when looked at from the basal side, larger 

 than the others, and the distal half of the above-mentioned uncalcified longi- 

 tudinal belt is generally very broad. 



The colonies have the same structure as in R. Schdiiaui, but the fenestrae 

 are very much smaller and generally much narrower than the segments between 

 them. 



Of this species I have examined a fragment from Torres Straits (Cambridge) 

 and one from Port Darwin (British Museum). 



R. reticulum Hincks. 



Flustra reticulum Hincks, 



Annals Nat. Hist. ser. 5, Vol. X, 1882, p. 163, PI. VII, fig. 4. 



(PI. XXII, figs. 1 a-1 c). 



The zooecia of rather varying form, most often irregularly pentagonal or 



hexagonal with an evenly rounded frontal edge. A cryptocyst appears as an 



extremely slight marginal expansion. The basal wall is uniformly, but no 



strongly calcified with the exception of a rather small, round (circular, oval or 



pear-shaped) uncalcified spot almost proximally to the distal wall. Very rarely 



a few short, coarse stripes appear here and there. Contrary to the case in the 



two other species the distal wall is generally straight in the ordinary zooecia, 



and it has about 10 uniporous rosette-plates, some of which are placed opposite 



