152 Rev. T. Hincks on the 
indicates affinity with the Schizoporellide. Should further 
examination show that the orifice in #lustra solida is dimor- 
phous, as it isin many of the Cheilostomata, and that the two 
forms which I have described are referable to one species, it 
will probably find a place in the above family. Unfortunately 
IT have only had immature fragments of the so-called “ smaller 
form,” and though they have enabled me to ascertain with 
accuracy the structure of its cell-mouth, they do not furnish 
the means of determining with certainty the relation between 
the two forms. 
A striking characteristic of PF. solida is the epidermal 
covering of a uniform greyish tint which invests the surface 
of the zocecia and occasionally of the ocecium also, though 
this is more usually free and retains its silvery lustre. The 
chitinous fibres which hold together the detached segments 
of the zoarium and also give origin to the organs of attach- 
ment are tubular extensions of the membranous covering of 
the cell * (PI. VIII. fig. 1c). 
Monoporella spinulifera, Hincks, var. (PI. VIII. fig. 3.) 
Mucronella spinulifera, Hincks, “Polyzoa of the St. Lawrence,” ‘Annals,’ 
May 1889, p. 431, pl. xxi. fig. 3. 
This species was described and figured in the last part of 
this series of papers; but I have since met with a strongly 
marked variety (Pl. VIII. fig. 3), which should not be passed 
without notice. 
Var. preclara.—Zowcia much larger than in the common 
form, more convex and deeply divided ; immediately below 
the orifice a large umbo, which frequently rises to a con- 
siderable height ; oral denticle wanting. 
The large size of the cell, the suboral umbo, and the 
absence of so distinctive a feature as the spinule on the lower 
margin materially affect the general appearance of the 
zoarlum. 
I have ranked this species in the genus Mucronella ; but on 
reconsideration I am inclined to think that its affinities are 
rather with Monoporella. 
Smitt has described and figured M. spinulifera + under the 
name Discopora cruenta, identifying it with the Lepralia 
eruenta, Norman, from which it differs essentially. He had 
* See a paper by the author, “On new Hydroida and Polyzoa from 
Barents Sea,” ‘ Annals’ for October 1880, p. 282. 
} “ Kritisk Porteckning ofv. Skandinaviens Hafs-Bryozoer,” Gufversigt 
al Kongl. Vetensk.-Akad. Forhandl. 1871. 
