NO. 2 OSBURN: eastern pacific BRYOZOA CHEILOSTOMATA 283 



the floor of the compensation sac that it is separated only with difficulty, 

 while the latter structure appears to be chitinized and spreads over the 

 whole width of the zooecial cavity, resembling the ectocyst of the Anasca. 

 Because of its simplicity this genus is tentatively assigned to the family 

 Hippothoidae, "a group of primitive Ascophora associated by their 

 simplicity rather than by more positive factors." 



The genus is named in honor of Thomas Hincks, the great English 

 bryozoologist who was the first to recognize spinulifera as a distinct 

 species. 



Hincksipora spinulifera (Hincks), 1889 

 Plate 33, figs. 1-+ 



Mucronella spinulifera Hincks, 1889:431. 



Monoporella spinulifera, Hincks, 1892 :152 (but not van praeclara). 



Porellina ciliata forma dura Smitt, 1867 :6. 



Discopora cruenta, Smitt, 1871 :1127. 



Lepralia cruenta. Waters, 1900 :73. 



Monoporella spinulifera, Norman, 1903:115. 



Mucronella spinulifera, Osburn, 1912a :282. 



Zoarium encrusting on shells in a single layer; reddish-brown, in 

 old colonies nearly black, the color all in the thick ectocyst. Zooecia 

 large, 0.65 to 1.00 mm long by 0.50 to 0.65 mm wide; separated by 

 deep grooves, the front arched, very thick, white and shining on the 

 removal of the ectocyst, with a row of conspicuous areolar pores. The 

 aperture is slightly broader than long (about 0.25 by 0.20 mm), rounded 

 distally and nearly straight on the proximal border; usually there is a 

 minute median spinule on the proximal border, but this is situated above 

 the level of the lyrula of Mucronella and not homologous with it ; occa- 

 sionally there are two or three spinules and often they are wanting. The 

 secondary peristome is a broad fold of the frontal which extends around 

 the lateral and distal sides of the aperture. Proximal to the aperture there 

 is occasionally a broad, low umbonate swelling, which sometimes shows 

 a rounded membranous area placed vertically on its distal face; this 

 may be a vestigial avicularium, but in my material I have not been able 

 to find positive evidence of a mandible. No oral spines, no dietellae. 



The ooecium is endozooecial, about 0.30 mm wide by 0.24 mm long, 

 the wall similar to the frontal, thick and granular; the peristome is 

 thicker on the sides and extends more or less around on the front of 

 the ovicell. 



