NO. 1 OSB URN : EASTERN PACIFIC BRYOZOA — CHEILOSTOMATA 111 



divide the opesia, the proximal part of which is slightly the larger. The 

 rostrum is somewhat variable in form but is shaped like a gothic arch, 

 slightly elevated and distinctly notched at the tip. 



The peculiar spicules are abundantly developed; the curved calipers 

 are of various sizes, ranging from 0.04 to 0.15 mm, and the wide open 

 arms of the compasses may measure as much as 0.50 mm but are usually 

 much smaller. 



Ovicells are wanting on our material, but Busk noted them on speci- 

 mens from Mazatlan, Mexico, the type locality. 



Hancock Station, 545-36, Puerto Refugio, Angel de la Guardia Is- 

 land, Gulf of California, one large colony covering a shell, shore collec- 

 tion. Also at Bahia San Francisquito, near Guaymas, Sonora, Mexico, 

 low tide, E. Yale Dawson, collector. 



Thalamoporella californica (Levinsen), 1909 

 Plate 12, fig, 2 



Thalamoporella rozieri var. californica, Levinsen, 1909 :184. 

 Steganoporella rozieri form gothica, Hincks, 1880:277. 

 Thalamoporella rozieri, Robertson, 1908 :277. 

 Thalamoporella californica, Hastings, 1930:716. 



The zoarium is at first encrusting, usually on algae, frequently rising 

 in erect, branching, articulated form; the free branches are divided into 

 internodes by chitinous joints. The zooecia are of moderate size, usually 

 between 0.50 to 0.65 mm in length by 0.30 to 0.34 mm in width, the 

 lateral walls nearly straight, the distal rim arcuate, conforming to the 

 aperture. The perforated cryptocyst extends for half or more of the 

 zooecial length, beyond which the imperforate roof of the polypide tube 

 rises sharply and forms the proximal border of the opesia. The opesiules 

 vary considerably in size and form, usually one larger than the other and 

 the descending wall of the larger one usually extends to the dorsal wall 

 where it forms a "shepherd's crook." The opesia is nearly round, about 

 0.18 mm in each dimension, arcuate but not sinuate on the proximal 

 border; the operculum thin with a broad chitinized border, the sclerite 

 on the proximal border strong at the sides, usually incomplete at the 

 middle. The adoral areas are always small, frequently wanting and when 

 tubercles are present they may be short and blunt, tall and thin, pointed 

 or tubular. 



The avicularia are nearly as long as the zooecia ; at the division of a 

 series ; the mandible is elongate and varies considerably in size and form. 



