48 Mr. A. W. Waters on Ghilostomatous Characters 



IV. — On Chilostomatous Characters in Mellcertitida3 and 

 other Fossil Bryozoa. By Akthur Wm. Waters. 



[Plate VI.] 



I HAVE on various occasions * pointed out that the Melicer- 

 titidaj have avicularia, and have also written to several friends 

 who were at work upon the Chalk fossils with the hope that 

 the relationship of this group would be thoroughly worked 

 out. Mr. Vine, however, in liis recent ' British Association 

 Report,' and Dr. Pergens, in his revision of d'Orbigny's 

 ' Cretaceous Bryozoa,' place them with the Cyclostomata 

 without indicating any doubt as to the position ; and it may 

 therefore be well to again call attention to some of the 

 characters of the group. 



When d'Orbigny wrote, " cellules accessoires " was a con- 

 venient term, as but little was known about avicularia ; and 

 in this family they are sometimes called '' cellules accessoires," 

 sometimes " cellules ovaricnnes ; " but it must be borne in 

 mind that also in Onychocella and its allies d'Orbigny did not 

 understand the function of the vicarious avicularia, which he 

 called " cellules accessoires," and speculated that since they 

 occur on the same zoaria as oviceils this could not be their 

 function, but might they be male cells ? Pergens, Marsson f, 

 and others, however, follow, and speak of triangular oviceils. 

 It is surprising that d'Orbigny should have called the organs 

 figured on plate 736. fig. 6, and plate 735, fig. 15, ' Paleon- 

 tologie Fran^ais,' oviceils, as they are so decidedly avicu- 

 larian in shape ; but as tliis is perhaps even more marked in 

 a specimen of Melicertites semiclausa^ d'Orb., in my collec- 

 tion, from Le Mans figures (1 and 8) are given. The 

 presence of a spatulate mandible is distinctly indicated, and 

 there can be little doubt that we have before us a vicarious 

 avicularium. In some cases the end of the mandible has 

 been unsymmetrical (fig. 8), similar abnormalities not being 

 unfrequent in recent vicarious avicularia. 



In M. royana, W. (fig. 2), there are also avicularia scat- 

 tered over the surface, and iiere again, if we are to judge by 

 analogy, we can scarcely doubt that in the beak there has 

 been a chitinous mandible. Tlie opening of the avicularium 



* Quart. Journ. Geol. Soc. vol. xl. p. 679 ; iS:c. 



t Mar.s.sou (' Die Bryozoen der weissen Sclireibkreicle der lusel Riigen,' 

 p. 47) makes Nodelea a genus of the family Eleidea, based simply upou 

 its having a special ovicell ; but his iigure of Nodelea prnpinqiut, 'Mara., 

 shows an undoubted avicularium and no ovieell. 



