261 



rib-like process starts on either side. These processes are situated immediately 

 within the proximal margin of the ectoooecium and thej' have a terminal por- 

 tion, which is bent upwards a little. 



The colonies form richly branched tufts, and the narrow columnar bifurcate 

 branches have four longitudinal rows of zooecia. 



Judging from descriptions and figures the forms hitherto described under the 

 name of Sinclairi present several differences from the form here described as well 

 as from one another, and only a comparative examination will show how great 

 an importance we ought to attach to these differences. For this reason I have 

 retained Busk's name for the form examined by me, which originates from 

 Akaroa Harbour, New Zealand (Suter). 



Under the names of 0. picoensis and 0. Grimaldi Jullien^ has described two 

 species, which seem to me to be very little different. In these the two small ro- 

 sette-plates between the aperture and the crescentic ascopore are said to be re- 

 placed by two small, round avicularia. As, however, avicularia have not hitherto 

 been made out with certainty in this family, this information needs further con- 

 firmation, as Jullien's figures are not convincing. 



Onchopora dentata Mac Gillivr. 

 Urceolipora dentata Mac Gillivray, Transact. Royal Soc, Victoria, 

 Vol. 21, 1884 (1885), pag. 109, PI. I, fig. 1. 

 (PI. XIII, figs. 6 a, 6 b). 

 The zoQBcia, which increase greatly in extent from their narrow proximal 

 part towards the distal end, are somewhat compressed, strongly arched and when 

 seen from the side of a triangular outline. Along the distal margin they are pro- 

 vided with 5 short, widely separated spines, which are rounded at the end and 

 surround the aperture. Thei-e are 6 transversely oval uniporous rosette-plates, 

 of which two are found between the aperture and the ascopore, while each of 

 the four others is situated between two spines. The operculum is almost semi- 

 circular with nearly parallel lateral margins, and the ascopore, which is con- 

 nected by a sutural line with the aperture, is but slightly curved with proxi- 

 mally directed concavity. The distal wall, which is bent from side to side, is 

 provided with a number of uniporous rosette-plates and terminates on either 

 side in 3—5 digitiform prolongations, of which the frontal is the longest. The 

 distal half of each basal wall has a large, pear-shaped, multiporous rosette- 

 plate. 



» 48, p. 52—53, PI. IV. 



