[323] THE BRYOZOA 23! 



The zoarium does not rise much above the substratum, but spreads 

 out in convoluted masses. From the point of origin of a colony, 

 smaller fronds spring, frequently overlapping the older ones, and the 

 whole has much the appearance of a brown lichen. The radical fibers 

 spring from the upper corner of the dorsal side of the zoecia (fig. 8, 

 r.f.). These frequently anastomose and form a network by which 

 the colony or frond is anchored. In some cases fibers from the dorsal 

 surface of an overlapping frond attach themselves to the margin of 

 the zoecia of the lower frond. Again, the lamina? are united back to 

 back. They are easily separable, however, and their union is effected 

 by means of short fibers. The margin of the distal part of the zoecium 

 is much elevated and the spines are very prominent (fig. 7). There 

 is considerable variation in their development, both in number and 

 size. The two horn-like ones at the top are always present. Below 

 these are usually two flattened ones on each side, which fold over the 

 zoecium just below the ovicell {Jl. sp.). Sometimes, however, there 

 are three flattened spines on each side, and again but one. Even on 

 the same frond these variations in number are found, as well as con- 

 siderable variation in size. No structure which could be called an 

 avicularium has been detected, although a considerable quantity of 

 material has been examined, both from Alaska and from Puget Sound. 



Family MEMBRANIPORID^. 

 MEMBRANIPORA Blainville. 



MEMBRANIPORA LACROIXII Andouin. 



Membranipora lacroixii HINCKS (*8o), pi. xvn, figs. 5-8. 

 Biflustra lacroixii SMITT ('72), Flor. Bry. pt. 11, pi. iv, figs. 85-88. 



Habitat. On shell. 

 Local distribution. Kadiak. 



Foreign distribution. Coasts of Britain ; Mediterranean ; coast of 

 Florida, 13-60 fms. ; St. Lawrence. 



MEMBRANIPORA MEMBRANACEA Linnaeus. 



Membranipora membranacea HINCKS (*8o), pi. xvin, figs. 5, 6. 

 Flustra membranacea JOHNSTON (*47). pi- LXVI, figs. 1-3. 



Habitat. Upon kelp forming circular patches. 



Local distribution. Yakutat ; Pribilof Islands, Alaska ; Queen 

 Charlotte Islands, incrusting stem of a seaweed. 



Foreign distribution. Universally distributed on the coasts of 

 Britain; Hvidingsoe; Hongesund; Roscoff; Adriatic; Lyalls Bay, 

 New Zealand ; Australia. 



