BEYOZOA. 105 



Olassiflcation.] 



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

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

 Eritoproda, 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, Phyladolcemata and Gymnolcemata, of ' Allman, into which it is 

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

 fossil marine f ormsr In the Phyladolcemata the lophophere is open on one side and 

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



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

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

 represented in the paleozoic rocks of America. 



SYSTEMATIC CLASSIFICATION OP PALEOZOIC BRYOZOA.* 



Sub-kingdom MOLLUSCOIDEA. 



Class BRYOZOA, Ehrenberg. 



Sub-class HOLOBRANCHIA, Ray Lankester. 



Order GYMNOLJIMATA, Allman. 



Sub-order CHILOSTOMATA, Busk. 



Orifice of zoceciutn situated laterally, of smaller diameter than the zocScium, 

 closed by a movable cover {operculum). Ova usually matured in external marsupia. 

 Appendicular organs (avicularia and vibracula) frequently present. 



Family Palescharid^, Ulrich. 

 Genus : Paleschara Hall. 



Family Worthenopoeid^, Ulrich. (Provisional) 

 Genus: Worthenopora Ulrich. 



Family PhaceloporiDjE, Ulrich. 

 Genus : Phaoelopora 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 upou the scheme iu vol. vili, III. Geol. Sur. Eep'ts. That oue 

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



