192 



tioned in Tli. (jrimnhila, Var. C, in which form il was only a conlinuation of 

 the polypide-lube. Most likely we have here a peculiar form of regeneration. 



Thalamoporella cincta Ihitlon. 



Membranipora cincta, HiiUon, l^rocccd. R. Soc. of Tasmania (1877), 



1878. 



Memhrani])ora transversa, Hincks, Annals Nat. Hist., ser. 5, Vol. VI, 



1880, p. 21, PI. XI, fig. 9. 



Diploi)ora cincta Mac Gillivray, Trans, and Proceed. H. Soc. of Victoria 

 (1880), 1881, Vol. XVII, p. 15, lig. 1 — 1 c. 

 (PI. XXII, lif^s. 7 a— 7 (I). 

 The zocecia, which are rather long and rectangular, have a length of 0,598— 0,6'"'"- 

 The large aperture, the size of which may be contained ;J7s — 4 times in the 

 whole length of the zoa-cium, has a broad and deep sinus, and the more or 

 less developed adoral areas have always acropetal spines, most frecjuently of a 

 somewhat compressed conical shape. The operculum, the concave proximal margin 

 of which is in the whole of its length furnished with a well developed chitinous 

 sclerite, has within each lateral margin a somewhat curved, chitinous ridge, which 

 on its internal side is proximally connected with a much shorter chitinous part, 

 distally ending in a small rounded expansion. Of the two opesiular outgrowths 

 only one reaches the partly or wholly uncalcified basal wall willi a shorter or 

 longer part of its proximal margin, while the other, which is very small and 

 sometimes difficult to distinguish from the frontal surface, only reaches the apper- 

 taining lateral wall. A little distally to the centre a short, but broad deepening 

 occupies the whole breadth of the frontal surface, and at the bottom of this 

 deepening the larger of the two opesiuhe is found on one .side and on the other 

 a deeply dej)resscd part of the polypidc-tube. The smaller of the two opesiulae is 

 generally situated immediately on the distal side of this deepening and in some 

 cases at its distal end. While the region between the aperture and the deepening 

 may be .sometimes quite smooth, sometimes with rather numerous tubercles, but 

 never with pores, the remaining part of the cryplocysl, which is extraordinarily, 

 sometimes almost rectangularly arched, is furnished with numerous tubercles and 

 small denticles in its distal i)arl and numerous pores in its proximal part. Also 

 the inner .surface of the lateral walls is very tuberculous and spinous. In the 

 proximal half of the zocrciuni each lateral margin expands into a strong, some- 

 what compressed but thick process with two arched lateral surfaces and of a 

 semi-circular or triangularly rounded outline. These processes, the outer surface 

 of which is distinctly transversely striated, are more or less inclined towards 



