6i6 



VAICHIRÔ OKA DA : 



ing of ovicells, as seen in ventral view, is broad and nearly 

 semicircular in shape, but, as the ovicells approach maturity, becomes 

 greatly narrowed owing to the downward growth of its arched upper 

 margin, which at the same time develops a weak peak in the middle, 

 somewhat as in R elongata Smitt or R. tessellata var. cocspitosa 

 Busk. 



A variation of certain constancy seems to exist in relation to the 

 depth of localities, with respect to the numbers of dorsal avicularia 

 and of barren trabecular present on the colonies. Both the structures 

 are much more numerously found on the specimens from Yodomi and 

 Onigasé than on those from the littoral of Misaki. While in the 

 latter the dorsal avicularia occur in a very limited number, in the 

 former they are profusely present, occurring, as they do, one to each 

 and every surface area surrounded by slightly raised vibices. 



2. Retepora misalciensis, n. sp. 



Pl. VIII., fig. I ; textfig. I. 



Zoarium erect, consisting of a number of wavy or flexuose and 

 irregularly infundibuliform growths arising from an incrusting disk ; 

 often with a short peduncle. Fenestrae irregular in size and shape, 

 measuring 1.9x0.8 mm. — 2.6x0.5 mm. large, usually three to four 

 times as long as wide, mostly rhomboidal, not infrequently very narrow ; 

 trabeculae 0.8 mm. wide on an average, nearly as broad as the width 

 of fenestrae. Zooecium oblong or irregularly rhomboidal, arranged 

 biserially in alternate arrangement, closely connate with one another 

 by lateral walls, and with smooth or nodulous ventral surface which 

 is freqeently perforated by two or three, small, circular pores. 

 Zooecial aperture semicircular, with thin margin and with oral fissure 

 at the middle of the lower margin. In the younger zooecia (textfig. 1 b), 

 the ventral zooecial wall slightly flares out at the rim of the aperture 

 and is thrown into some longitudinal folds, in the adjoining part. Oper- 



