NO. 1 OSBURN : EASTERN PACIFIC BRYOZOA — CHEILOSTOMATA 109 



Labioporella sinuosa Osburn, 1940 

 Plate 11, fig. 12 

 Labioporella sinuosa Osburn, 1940 :377. 



Zoarium encrusting rather loosely on various surfaces, yellowish to 

 light brown, white and glistening in the absence of the ectocyst. Zooecia 

 with sinuate lateral walls when crowded or on rough surfaces, but per- 

 fectly regular and with parallel walls when growth conditions permit. 

 The walls are elevated, the mural rim delicately beaded, the inner border 

 of the walls coarsely beaded even on the distal wall, Gymnocyst wanting. 

 The cryptocyst covers the entire proximal chamber with a thick, per- 

 forated and granulated layer, which ceases abruptly at the descending 

 lamina. Distal to this the cover of the polypide, longitudinally rugose, 

 with the tip elevated and finely crenulate, projects for a short distance; 

 this is connected with the lateral walls by a narrow shelf which is im- 

 perforate. The descending lamina of the cryptocyst is vertical, straight, 

 complete except for the perforation of the polypide tube, and divides the 

 zooecial cavity into two subequal chambers. The distal wall is slightly 

 arched on the dorsal side, strongly on the frontal side and overlies the 

 base of the distal zooecium; on the proximal side of the distal wall just 

 beneath the tip of the operculum is a distinct rounded tubercle. The 

 operculum is longer than wide (0.15 by 0.13 mm), with a dark brown 

 border sclerite, widely separated from the walls on the sides but nearly 

 touching the distal wall. Multiporous septulae present. No ooecia. No 

 ovicularia have been observed in either Atlantic or Pacific specimens from 

 various localities. 



Originally described from the Tortugas Islands, Gulf of Mexico, the 

 species proves to be well distributed on the Pacific coast from the Gulf 

 of California to Ecuador. It appears to be nearly related to L. spatulata 

 Harmer, 1926:283, but it differs from Harmer's description and illustra- 

 tion (pi. 21, fig. 6) in the presence of coarse crenulation on the inner 

 border of the walls, even around the distal end ; in the form of the 

 operculum which is noticeably longer; the descending lamina is always 

 simple, and the tubercle beneath the operculum is never doubled or 

 tripled. The complete absence of avicularia renders it difficult to ally this 

 form with any of the other species, which have been described from Cey- 

 lon, Australia, the East Indian region and Japan. Possibly the absence 

 of avicularia may be a specific character, since none have been found 

 throughout the range on either coast. 



Hancock Stations: 596-36, 599-36, 637-37, 650-37 and Albatross sta- 



