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



but it would seem that he must have examined some broken down specimens. I pro- 

 pose to call this a concealed ovicell, 'retaining the expression immersed for those which 

 give an external indication of their presence. 



The bridge between the two lateral avicularia rises up into a kind of mucro, turning, 

 however, at right angles to the axis of the zoarium, and projecting but little over the 

 aperture. In the specimen examined there is a semitransparent membrane covering the 

 whole surface. 



Schizoporella challengeria, n. n. (PI. IT. figs. 25-28). 



Myriozoum immersum, Busk, Zool. Chall. Exp., part xxx. p. 170, pi. xxv. fig. 4. 

 TTspecimen from Station 820, 600 fathoms, shows that Mr. Busk never saw the oral 

 aperture, and in fact it never can be seen except on a broken surface or in section, since it 

 is placed nearly at right angles to the axis of the zoarium, instead of being parallel as usual. 

 What Mr. Busk took for the oral aperture and figured (4 c) is only the lower part of the 

 secondary orifice, and the tube leading to the avicularium projects into this immersed 

 peristome, causing the appearance which misled Mr. Busk. This I show in section in 

 fig. 27. Another point of veiy great interest is the discovery of a concealed ovicell 

 opening into the peristomial tube (see fig. 25). Only a small fragment, however, was 

 available for making a section, and this point should be further studied in young growing 

 branches, but I think my interpretation will be found correct. It should, however, be 

 noticed that the cavity is below the peristome, and not above. As OncJiopora immersa, 

 Plaswell, would seem to be Schizoporella, it is requisite to change the name. 



Schizoporella vitrea, MacGillivray (PI. III. figs. 31, 46). 



Lepralia vitrea, MacGillivray, Zool. of Vict., dec. iv. p. 32, pi. 38, fig. 4. 

 Lepralia incisa. Busk, Zool. Chall. Exp., part xxx. p. 145, woodcut, fig. 42. 



There is already Lepralia incisa, Reuss, but the Challenger form is no doubt the 

 Schizoporella vitrea of MacGillivray. In some parts of the colony the zocecia are oblong 

 with straight sides, in others the zocecia may be called oval. In well-preserved parts 

 the surface appears covered with white spots, and in the centre of each is the pore. The 

 avicularia are acute, and not " oval." The ovicell is round, raised, but partly immersed 

 in the zocecium above, and with a granular surface. 



Habitat. — Station 135a, ofl' Inaccessible Island, 75 fathoms ; Williamstown (Victoria). 



Myriozoum marionense, Busk. 



Myriozoum marionense, Busk, Zool. Chall. Exp., part xxx. p. 171, pi. xxiii. fig. 6. 

 Through Miss Busk's kindness, I have been able to examine specimens from three 

 localities, and see that they are in no way similar to my Porina {?) inversa, as I at one 



