of the Cheilostomatous Polyzoa. 17 



their base and are best developed on the back wall. They are 

 also present on the front wall, where, however, the epitheca is 

 mainly held in position by those parts of the zooecia which im- 

 mediately surround the opercula. Many Cretaceous species were 

 probably provided with an epitheca which was stretched at a 

 distance from the zooecia, as is indicated by the occurrence of 

 similar papillae 1 . 



[Dec. 13, 1900. — During the correction of my proofs I have 

 received an important memoir, " Contribution a l'histoire naturelle 

 des Bryozoaires Ectoproctes " (Trav. Inst. Zool. Montpellier, N.S., 

 Mem. No. 8, 1900), kindly sent to me by the author, M. Louis Calvet. 

 I can do no more, on the present occasion, than to call attention to 

 the fact that M. Calvet, on p. 278, discredits Jullien's account of 

 the compensation-sac, and suggests that the existence of strong 

 parietal muscles indicates that the calcareous front wall is flexible 

 in Lepralioid forms. My own observations, on the contrary, show 

 clearly that the parietal muscles are inserted into the floor of a 

 ^compensation-sac] 



1 Cf. D'Orbigny, torn, cit., PL 718, 'figs. 3, 7, 10, 11, 15; PL 721, figs. 3, 4, 7, 8 ; 

 etc. 



VOL. XL PT. I. 



