256 BRTOZOA 



lines to deep water, from Long Island Sound to the Arctic Ocean; very 

 common; cosmopolitan. 



M. monostachys Busk. Colony irregular, often radiate; zooecia oval 

 and elongate, with usually 6 to 10 pairs of marginal spines, of which the 

 upper pair is directed upwards and the others bend inwards, often meet- 

 ing in the middle; a single large basal spine is directed forwards and 

 may be the only spine present; avicularia wanting; ooecia wanting: on 

 stones, shells, seaweed, etc., from shallow to deep water; New Jersey to 

 the Arctic Ocean; cosmopolitan. 



M. craticula Alder. Zooecia small, in regular radiating linear rows, 

 oval; margin with about 14 flattish spines, of which the upper 2 are 

 erect; the others extend across the cell, meeting in the middle of it; an 

 avicularium often at the margin of the cell: on shells, etc., the colony 

 forming small flabellate or roundish patches with a spongy appearance; 

 from shallow to deep water; Arctic Ocean to Long Island Sound. 



FAMILY 8. CEIBEILINIDAE. 



Colony incrusting or erect; zocecia with the front wall more or less 

 fissured or traversed by radiating furrows : 6 genera. 



CRIBRILINA Gray. Colony incrusting; zocecia contiguous; opening 

 semicircular: about 20 species. 



C. punctata (Hassall). Zooacia oval, covered with small punctures, 

 often arranged in rows; 4 or 5 marginal spines with usually an avicu- 

 larium on each side of the orifice ; ocecia rounded : Vineyard Sound and 

 northwards ; in shallow water ; common on shells and pebbles ; Europe. 



C. annulata (Fabricius) (Fig. 418). Zooecia ovate, convex, very 

 distinct, with a median keel and about 6 transverse rows of punctured 

 furrows; sometimes with 3 or 4 marginal spines; colony forming small 

 reddish crusts: on stones and kelp, from shallow to deep water; often 

 common north of Cape Cod; Europe. 



FAMILY 9. MICEOPORELLIDAE. 



Colony either incrusting or erect and foliaceous or dendritic; orifice 

 more or less circular and with a straight lower margin and a semilunate 

 or circular median pore immediately below it : 3 genera. 



MICROFORELLA Hincks. Colony incrusting; orifice semicircular: 

 several species. 



M. ciliata (Pallas) (Fig. 419). Colony forming a delicate, irregular 

 crust with a frosty sheen on seaweed, shells, etc.; zooecia obscurely hex- 

 agonal and punctate; orifice bearing 3 to 7 long spines, which may be 

 wanting; median pore lunate; large avicularium on one side with an acute 



