NO. 1 OSBURN: eastern pacific BRYOZOA CHEILOSTOMATA 177 



mere stubs or absent. There is a peculiarity in the distal pair of spines, 

 the bases of which are continued forward to form the lateral borders of 

 the aperture; these are fairly regular but other spines vary widely in 

 form, size and amount of fusion. 



No ovicells have been observed. No oral spines, no avicularia, no 

 dietellae. 



Described from the Gulf of St. Lawrence (Hincks), and reported 

 from Shoal Tickle, Labrador (Osburn). The occurrence of this species 

 from northwestern Alaska indicates that it is probably circumpolar in 

 distribution. 



Point Barrow, Alaska, 20 fms, G. E. MacGinitie, Arctic Reasearch 

 Laboratory, common and forming large colonies. 



Genus CRIBRILINA Gray, 1846 

 Costules generally closely attached throughout their length, leaving 

 lacunae of various sizes (more or less irregularly spaced in the type). 

 Ovicell hyperstomial and closed by the operculum. The proximal rim of 

 the orifice often with a mucro. Avicularia, when present, at either side of 

 the orifice. Dietellae present. Genotype, Lepralia punctata Hassall, 

 1841:368. 



Gribrilina annulata (Fabricius), 1780 

 Plate 28, fig. 7 

 Cellepora annulata Fabricius, 1780:436. 

 Cribrilina annulata, Osburn, 1933 :32. 



Not C. annulata, Robertson, 1900:280 (see Lyrula hippocrepis) . 

 Cribrilina annulata, O'Donoghue, 1923:30; 1926:50. 



The zoaria encrust shells and stones, forming small rounded colonies 

 of a reddish or brownish color," pulcherrimaet perfectissimahaec omnium 

 visarurn" (Fabricius, Cellepora annulata, 1780:436). 



The zooecia vary greatly in size, 0.45 to 0.65 mm long by 0.30 to 

 0.40 mm wide, and in addition the ovicelled zooecia are often much re- 

 duced. The pericyst is formed by about 8 pairs of costae which are trans- 

 verse distally but radiate at the proximal end; the costae are separated 

 by rather deep grooves which extend across the whole of the front, ex- 

 cept when interrupted at the median line by a low carina. In the grooves 

 on each side there are about 4 (3 to 6) small rounded lacunae. The 

 distal pair of costae form the proximal border of the aperture which 

 usually bears an umbonate process more or less developed. The aperture 

 is transverse (about 0.18 mm wide), somewhat semicircular, and on 

 each side is a short strong spine ; a pair of similar but somewhat smaller 

 spines at the distal corners. There are no avicularia. 



