50 Mr. A. W. Waters on CInlostomatous Characters 



and other species of Cyclostomata, caused by the walls being 

 thinner where the perforations occur. 



Dr. Ilann* placed tlie Melicertitidas as a third " typus" (the 

 Stigmatoporina) of thelnarticulata,a"tribus" of theCyclosto- 

 mata, on account of the mode of growth, namely the zooecia ter- 

 minating at right angles to a central bundle of long parallel 

 tubes. Marssont divides the Cyclostomata into typus Soleno- 

 porinaand typus Metopoporina, the last including the families 

 Ceidea, d'Orb., and Eleidea, d'Orb. Pergens + makes a typus 

 Melicertitina. Each of these workers calls attention to the 

 trumpet-like dilation of the extremity of the zooecia, but all 

 speak of the triangular ovicell, though if we are to be guided 

 at all by analogy there is no reason for speaking of an ovicell, 

 whereas the resemblance to many undoubted vicarious avicu- 

 laria is most striking, for there is evidently the platform for 

 a triangular or spatulate chitinous appendage. 



Before we can be sure of the position of this division, or 

 perhaps suborder, the whole group must be reexamined, as 

 probably some of the forms placed here by d'Orbigny should 

 simply be removed to Chilostomata, others remaining with 

 the Cyclostomata, leaving a division which should be care- 

 fully compared with some of the older forms, and perhaps 

 some Palteozoic fossils will be elucidated thereby. 



To come to the second part of the paper, E. 0. Ulrlch § 

 has recently published an important work on the Palasozoic 

 Bryozoa of Illinois, and considers that the suborder Crypto- 

 stomata of Vine shows relationship with the Chilostomata ; 

 and this publication has induced me to put together the above 

 results, which, like many other fresh facts, have been among 

 my notes for many years. Ulrich lays great stress upon two 

 projecting processes in the interior of the Cryptostomata, 

 which I pointed out as existing in a species of Fenestellidse |i 

 and which Ulrich now calls hemisepta. These are usually at 

 the base of what Vine and Ulrich call a vestibule; that is to 

 say, there is within the shell a tubular shaft up to the external 

 opening, so that it is at right angles to the '' primary cham- 

 ber," whi(;h might be called the zooecial chamber. No 

 explanation is attempted of the function of the hemisepta; 

 but there are a great many recent species in which there is a 

 similar vestibule, at the base of wliich is the oral aperture 



* ' Die Bryozoen des Mastrichter Ober Senon.' 



+ ' Die Bryozoen der weisseu Schreibkreide der Insel Riigen,' p. 7. 



I " Revision des Bryozoaires du Cretace figures par d'Orbigny," Bull. 

 See. Beige de G^o!. vol. iii. 



§ " Palaeozoic Bryozoa," Palaeontology of Illinois, vol. viii., 1890. 



II " Remarks on some Fenestellidae," Manchester Geol. Soc. vol. xiv., 

 1878. 



