24 THE VOYAGE OF H.M.S. CHALLENGER. 



Mucronella canalifera, Busk (PI. III. fig. 44). 



Mucronella canalifera, Busk, Zool. Chall. Exp., part xx.x. p. 1.59, pi. xxii. fig. 2. 



There are several specimens from washings between Fayal and Pico. 



The rule seems to be eight oral spines, and the lower edge of the aperture is nearly 

 straight with two minute lateral denticles, giving the aperture the same character as that 

 of Cellepora alhirostns. I do not see any Mucronellidan character, and peristomial 

 ones have never seemed to me satisfactory for generic divisions. There seems to be a 

 I'elationship to Lepralia. 



Mucronella contorta, Busk (PI. I. fig. 24 ; PI. III. fig. 30). 



Mucronella contoiia, Busk, Zool. Chall. Exp., part xxx. p. 155, pi. xx. fig. 9. 



In the specimen from Simon's Bay there are small round avicularia replacing m.any 

 of the pores. In a specimen from Algoa Bay, in my collection, these round avicularia 

 are still more numerous, in some cases there being as many as seven to a single zooecium. 

 There are three distal rosette plates, and there is a round calcareous process on each side 

 of the aperture, projecting into the interior of the zooecium, for the support of the 

 operculum. In my Algoa Bay specimen there are very few of the large avicularia by the 

 side of the aperture, but there is usually a small one on each side nearer to the 

 operculum. The operculum is very characteristic, having a thick band crossing it 

 transversely. The " mucro " of Mucronella occurs in very various ways, and I cannot 

 see that the small projection, which we may call a lip in the present case, can be used as 

 a generic character. 



It seems that Mucronella may with advantage be dropped, and some, as the above, 

 be placed with Lepralia, and the rest mostly show aflSnity with Smittia. 



Bracehridgia geometrica, Reuss. 



Biflustra geometrica, Renss, Foram. Aiith. und Bryozoen des deutschen Septarienthones, Denkschr. 



Akad. Wiss. Wien, Bd. xxv. p. 189, Taf. vi. fig. 16. 

 Porella emendata, "Waters, Quart. Journ. Geol. Soc, vol. xxxvii. p. 336, pi. xvii. fig. 69. 

 Miicronella pyriformis. Busk, Zool. ChalL Exp., part xxx. p. 155, pi. xx. fig. 5. 

 Bracehndcjia pijrifonnis, MacGillivray, Trans. Roy. Soc. Victoria, vol. xxii. p. 8 (sep.), pi. ii. 

 figs. 6, 7; Zool. of Vict., dec. xvi. p. 219, pi. 158, figs. 6-8. 



In the Challenger .sjDccimens the row of pores round the edge of the zooecium can be 

 seen, entirely corresponding with those figured in the fossil, and in size the Australian 

 fossil and recent are identical, though in the Challenger specimens I did not find any of 

 the small diagonal avicularia. In one case, however, there was an appearance suggesting 

 a broken down one. Also in the recent specimens from Victoria these avicularia are very 



