19*^^] Robertson. — Incrusting Bryozoa. 275 



zooecia. and also many colonies in which zooecia possessing both 

 typos of ornamentation occur, both that characterizing the youth- 

 ful stages (fig. 25) and that found in the adult stage (fig. 22), 

 so that no doubt can exist that we have here the metamorphosis 

 of the Cyp]i())i(iiitcs of M. viJlosa. 



Microporidae Smitt. 



Micropond(e Smitt, 1873. 

 Membramporidcp, (part) Busk, 1854. 

 MicroporidcF, Hincks, 1880. 



Zooecia with front wall depressed, calcareous margins ele- 

 vated. 



Micropora Gray. 



Flustra, (part), Johnston, 1847.. 

 Micropora Gray, 1848. 

 Discopora (part) Lamarck, 1856. 

 Membranipora, (part), Busk, 1854. 

 Micropora, Smitt, 1873. 

 Micropora, Hincks, 1880. 



Zoarium incrusting. Zooecia with prominent raised margins; 

 front wall depressed, wholly calcareous; orifice semi-circular or 

 suborbicular, inclosed by a raised calcareous margin. 



47. Micropora coriacea Esper. 



PI. 17, fig. 26. 



Flustra coriacea Esper, 1791-97, pt. 7, fig. 2. 



Membranipora coriacea, Busk, 1854, pt. 2, p. 57, pi. 73, figs. 4, 5. 



Micropora coriacea Gray, 1848. 



Discopora coriacea, Lamarck, 1856, ed. 2, vol. 2, p. 251. 



Micropora coriacea, Smitt, 1873, pt. 2, p. 13, pi. 3, fig. 74. 



Micropora coriacea, Hincks, 1880, p. 174, pi. 23, figs. 5-7. 



Zoarium forming a delicate incrustation on shells, other bry- 

 ozoa, etc. Zooecia elliptical or rhomboidal (pi. 17, fig. 26) ; mar- 

 gin slightly roughened, raised, sometimes slightly thickened on 

 each side just below the orifice ; front wall minutely granular and 

 punctate, freciuently possessing a foramen, for., a more depressed, 

 thinner portion of the front wall on each side just below the ori- 

 fice. Orifice broader than high, its upper margin semi-circular, 

 its lower margin straight, projecting slightly outward. Occa- 

 sionally a small avicularium just above the orifice, placed some- 



