316 



GENUS II. PARACYATHUS (M. Edw. & Haime). 



Corattum simple, subturbinate or cylindrical, with 

 an expanded base, permanently adherent. 



Columella very broad, terminated by a papillous 

 surface, and formed by processes that appear to arise 

 from the lower part of the inner edge of the septa. 



Palules of divers orders, forming two or more 

 circles ; in general lobed at the summit, narrow, tall, 

 and appearing also to arise from the lower part of the 

 inner edge of the septa, their size diminishing as 

 they approach the columella. 



Plates nearly equal, very slightly salient, and 

 closely set ; their lateral surfaces strongly granulated, 

 and sometimes presenting traces of imperfect dis- 

 sepiments. They form four or five cycles, and the 

 systems are equally developed. 



Bids nearly equal, straight, closely set, projecting 

 very little, and delicately granulated. 



ANALYSIS OF BRITISH SPECIES. 



Plates forming five imperfect cycles : cup elliptical . . . Taxilianus. 

 Plates forming four imperfect cycles : cup circular . . . 



Ribs obsolete below TJiulensis. 



Ribs very salient below pteropus. 



