CELLEPORA COSTAZII. 413 



is orbicular, and there is a well-marked sinus below ; as 

 growth advances, however, it is more or less concealed by 

 the elevation of the peristome, which usually forms a thin 

 and shallow rim or border round the front. In the verv 

 curious and interesting variety {tuhulosa) , the peristome is 

 prolonged into a suberect tubular shaft, Avithin which the 

 orifice is deeply sunk. In this form the tubular extension 

 of the peristome rises above the ovicell, which is situated 

 behind it. In old specimens, in which the ooecia are 

 freely developed, the species takes on a different and 

 very picturesque appearance. In some cases the inclosed 

 area on the front of the ooecium is perforated with large 

 punctures ; in others it is simply furrowed. This is a 

 trifling difference, the furrowed condition being probably 

 due to the confluence of the pores. 



The cells are smooth and generally dull and opaque ; 

 but in some forms they are of a more delicate texture and 

 almost hyaline. 



Though the list of localities is comparatively small, C. 

 Costazii is, I believe, a common species. It occurs abun- 

 dantly on the stems of various Hydroid zoophytes, over 

 which it spreads in minute colonies. 



\TIie following genus should have been placed amongst 

 the Porinidfe, yage 226.] 



Genus CELLEPORELLA, Gray. 



Der. Dim. of Cellepora, a genus of Polyzoa. 



Generic Character. — Zocecia suberect, the anterior 

 extremity tubular and free, with a terminal circular orifice. 

 No special pores. Zoarium {in the British species) in- 

 crusting. 



