1908] Robertson. — Incrusting Bryozoa. 281 



Microporella Ilincks. 



Eschara, (part) Pallas, 1766. 

 Lepralia (part) Johnston, 1847. 

 Lepralia (part), Busk, 1854. 

 Eeptoporina d'Orbigny, 1850-52. 

 Porellina Smitt, 1873. 

 Microporella Hincks, 187-7. 



Zoarium incrusting. Zooecia with a semi-circular orifice, the 

 loM'er margin entire, and a semilunar or circular pore below it. 



50. Microporella calif ornica (Busk) Hincks. 



PI. 18, figs. 32, 33, 34. 



Lepralia californica Busk, 1856, p. 310, pi. 11, fig. 6. 

 Microporella ciliata form californica, Hincks, 1883, p. 444, pi. 17, 

 fig. 3. 



Zoaria forming spinous patches on seaweed (pi. 18, fig. 32). 

 Zocecia ovate or rhomboidal, separated by well marked sutures, 

 alternate (fig. 33) ; front wall convex, calcareous, punctate. Ori- 

 fice arched above, lower margin straight; upper margin sur- 

 rounded by six or seven long spines, in some cases small and dark 

 in color ; below the orifice an oval or sometimes obscurely lunate 

 pore filled in with a fine sieve-like plate (fig. 34) ; the pore fre- 

 quently hidden more or less by an umbonate process (fig. 33, 

 urn. pro.) developed just below it; or the pore may be somewhat 

 elevated. On each side of the pore a sessile avicularium with 

 mandible directed obliquely upward or slightly outward. Ooecia 

 globose, of medium size, punctate, where spines are present on the 

 zooecium, the lowermost pair visible in front of each ocecium. 



Hincks regards this as a form of the cosmopolitan species M. 

 ciliata and reports it as abundant at Queen Charlotte Islands. 

 The chief differences between M. californica and the typical M. 

 ciliata lie in the posses.sion by the former of an avicularium on 

 each side of the median pore instead of upon one side only, and 

 in the structure of the plate covering the pore. In ill. ciliata the 

 pore is semilunate, the inner edges of the crescent being furnished 

 with fine teeth, the whole strongly resembling the pore of M. 

 malusi (fig. 35, p.). In M. californica the pore is large, oval, and 



