a2 ON THE SILURIAN SPECIES OF GLAUCONOME. 
that Chilostomatous types existed in Paleozoic times. The majority . 
of these older species will be found to arrange themselves under the 
Cyclostomata ; the rest will be accommodated in the new suborder 
Cryptostomata. 
Class POLYZOA. 
I. Suborder Catnostomata, Busk. 
“Orifice of the zocecium closed by a movable opercular valve. 
Ova usually matured in external marsupia. Appendicular organs 
(avicularia and vibracula) frequently present.” Hincks. 
Very few species at present known to us in the fossil state. It 
is doubtful if they are found below the Cretaceous period. 
II. Suborder Crctosromata, Busk. 
** Zocecia tubular, with a plain inoperculate orifice. Marsupia and 
appendicular organs wanting.” Hincks. : 
Species belonging to this suborder less specialized than recent 
types range from the Lower Silurian upwards. 
III. Suborder Cryprostomata, Vine. 
Zocecia subtubular, in section slightly angular. Orifice surrounded 
by a vestibule, or otherwise concealed. 
To this division we assign the Silurian species of Glauconome and 
Ptilodictya. 
Discussion. 
Prof. Hues bore testimony to the valuable work which the 
authors were accomplishing in connexion with the study of a very 
difficult group of organisms. 
