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A REVISION OF THP: aRNUS STEGANOI'ORELLA. 291 



A opercula Avitli a pair of strong 



teeth on the main sclerite, just 



distal to the occlusor tubercle. 



B opercula convex distally,with 



a series of strong, slightly 



curved, suberect teeth . . 10. S. truncata. 



A opercula rare, without teeth, b 



opercula transversely oblong, 



with six to eight strong curved 



submarginal teeth distally, and 



two or three others on each 



side; the teeth fitting into 



sockets in the calcareous zooe- 



cium . . . . . 12. S. alveolata. 



r A with submarginal teeth; those of 

 , I B much stronger distally than 



I proximally . . . 11. S. raagnilabris. 



I A toothless, " undifferentiated " . 7 



"" iSubmarginal teeth of b long, fine, 



restricted to the distal half of 



the operculum, b zooecia about 



twice as lars'e as a zooecia , 8. S. Haddoni. 

 I Submarginal teeth of B small, the 

 I series commencing in the prox- 



I imal half. B zooecia not twice 



L as large as a zooecia . . 9. S. Bnskii. 



J 



Cryptocyst inserted at or near the 

 base of the distal wall ; zooecia 



< 



of large size 



Cryptocyst inserted into the basal 

 wall at n, distance from the 

 distal wall ... . 10 



