l-'08] Kobertson. — IncrustiiKj Bnjozoa. 295 



crusting colonies, but soon grow into stiff, upright, branching 

 stems (pi. 21, fig. 57). The older portions of these colonies be- 

 come highly calcified, and the active zooecia are found only at the 

 rounded tips of the branches. The arrangement of the zocecia in 

 such stem is regularly alternate around a central core (fig. 56). 

 The inner zoo'cial walls have an extremely delicate finely porous 

 structure, while the external M-alls are generally more coarsely 

 porous or reticulated. 



64. Myriozoum crustaceum Smitt. 



PI. 21, fig. 54. 



Myriozoum crxistacetim Smitt, 1867, p. 18, pi. 25, figs. 88-91. 

 Myriozoum crustaceum, Eobertson, 1900, p. 327. 



Zoatium incrusting, often growing in several layers one on top 

 of the other. Zooecia immersed, lines of separation not visible, 

 front wall thickly punctate, or in a younger stage, reticulate (pi. 

 21, fig. 54). Orifice rounded above, the lower margin possessing 

 a well marked sinus. Usually a small avicularium, av., on each 

 side of the orifice, sometimes on one side only. Ooccium of mod- 

 erate size, sub-immersed, bordered with a row of pores and thick- 

 ly punctate. 



This species has been obtained at Yakutat, Orca, Kadiak and 

 Juneau on the coast of Alaska. 



65. Myriozoum coarctatum Sars. 



PI. 21, figs. 55, 56, 57. 



Myriozoum coarctatum Sars, 1851, vol. 6, p. 148. 

 Myriozoum coarctatum, Smitt, 1867, p. 18, pi. 25, fig. 92. 



Zoarium ramose, attaining a height of 75 to 100 mm. ; branch- 

 ing dichotomous. Zooecia immersed, alternate, front wall thickly 

 covered with large pores (pi. 21, fig. 55) . Orifice, or., higher than 

 broad, rounded above, lower margin possessing a well formed 

 sinus. Avicularia wanting. Ooeciaf 



This species is reported by Hincks from Queen Charlotte Is- 

 lands. Dredged at 20 fathoms at Juneau ; found also at Orca 

 and Yakutat, Alaska. 



