ioioj Robertson: Gyclostomatous Bryozoa. 235 



tin' chitinous septum occurs in thi icium of C. franciscana, a 



cellular septum i urs in C. edwardsiana formed by a layer of 



high columnar cells which as arc seen in cross-section spread in 

 a fan shape forming a semicircle (pi. 18, fig. 5, sep.). Prom 



it there depends, as in other cases, a delicate, ehitii s tube, and 



above it then' extends from side to side a continuation of this 

 chit im ins tissue form inn a chitinous floor t rlii. //. i . Whether this 

 floor is perforated or not has not been ascertained. 



The function of this septum, either chitinous or cellular, is 

 not clear. It can hardly be said to be for the purpose of 

 strengthening the ooecial wall at that point, since the species 

 whose ovicell appears most to need support has merely a cellular 

 septum. Its function seems to be most closely related with that 

 of the inner chitinous tube, and in two species, with the chitinous 

 floor, acting as the means of attachment and support for it. 

 Thus, by reducing the size of the opening into the ocecial tube in 

 ('. franciscana, and by supporting a chitinous floor in C. geni- 

 culata and C. edwardsiana, the septum may directly in the first 

 case, indirectly in the other two cases, prevent the larvae in 

 their circulation through the ovicell from passing into a culdt sac 

 from which they might be unable to extricate themselves. 



C. franciscana is abundant between tide marks at Fort Point and 

 Lands End, San Francisco; also at Dillons Beach, Navarro, and Pacific 

 Grove. California. Found also at low tide at Puget Sound, the colonies 

 of more delicate appearance than are those obtained further south; 

 also at Orca, Alaska, growing on worm tubes. Found on the shore 

 rocks at Ballast Point, Coronado, California, and dredged at numerous 

 stations on the coast of Southern California in depths ranging from 2 

 to 19 fathoms. 



85. Crisia geniculata Milne-Edwards. 



PI. 18 and 19, figs. 6, 7, and 8. 



Crisia geniculata Milne-Edwards, 1838, vol. 9, ser. 2, p. 197, pi. 6, figs, I 



I'. I", I'. 

 Filicrisia geniculata, d'Orbigny, 1851, p. Cin4. 

 Wrisiilia gracilis Trasji, L857, p. 113, pi. 5, fig. 3. 

 Crisia cornuta a, sine cornibus, Smitt, 1865, pp. 115 and 126, pi. 10. fijjs, 



2, 3. 

 Crisia cornuta, var. B, geniculata, Busk, 1875, p. 3, pi. I, figs. 1-4. 

 Crisia cornuta, var. A. geniculata, Hincks, 1880, p. 419, pi. 56, fig. 4. 

 Crisia geniculata, Banner, 1891, p. 170, pi. 12, figs. 7 and 8. 



