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, tom. cit ., PL 718, figs. 8, 7, 10, 11, 15; PI. 721, figs. 3, 4, 7, 8 ; 
etc. 
VOL. XI. PT. I, 
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