BRYOZOA. 105 



Classifloation.] 



According to Nitsche the Holobranchia are again divisible into two very unequal 

 groups, the Ectoprocta, in which the lophophore surrounds the mouth only, and the 

 Entoprocta, in which it encloses both the orifices of the alimentary canal. 



The former division embraces the great majority of the Bryozoa, and the second 

 of the two orders, Phylactoltemata and Gymnolcemata, of Allman, into which it is 

 almost universally divided, comprises, with very few exceptions, all the living and 

 fossil marine forms. In the Phyladokemata the lophophere is open on one side and 

 horseshoe-shaped ; in the Gymnokcmata it is complete and circular. 



The second of these orders has been divided into five suborders, the Chilostomata, 

 Cryptostomata, Trepostomata, Cyclostomata, and Ctenostomata, all of which seem to be 

 represented in the paleozoic rocks of America. 



SYSTEMATIC CLASSIFICATION OF PALEOZOIC BRYOZOA.* 



Bub-kingdom MOLLUSCOIDEA. 



Class BRYOZOA, Ehrenberg. 



Sub class HOLOBRANCHIA, Ray Lankester. 



Order GYMNOL^MATA, Allman. 



Sub- order CHILOSTOMATA, Busk. 



| 



Orifice of zocecium situated laterally, of smaller diameter than the zooecium, 

 closed by a movable cover (operculum). Ova usually matured in external marsu.pia. 

 Appendicular organs (avicularia and vibracula) frequently present. 



Family PALESCHARID.S;, Ulrich. 

 Genus : Paleschara HALL. 



Family WOHTHENOPORID^E, Ulrich. (Provisional) 

 Genus : Worthenopora ULRICH. 



Family PHACELOFORID.*:, Ulrich. 

 Genus : Phacelopora ULRICH. 



Suborder CRYPTOSTOMATA, Vine. 



Primitive zocecium as in the Chilostomata. Orifice concealed, at the bottom of a 

 tubular shaft or vestibule, which may become intersected by straight diaphragms or 

 hemisepta through the direct super-imposition of successively developed layers of 

 polypides. External orifice rounded, often closed by a perforated or entire cover. 

 External marsupia and avicularia wanting. 



The classification here published is a slight improvement upon tlio scheme In vol. viii. 111. Geol.Sur. Kep'ts. That ..in- 

 represented the stuff of our knowledge on the subject in 1887-89. 



