VI 



Marginal (or oral) spines. Spines issuing from tlie inner margin of a gymnocyst. In 

 very rare cases {Crepidacantha Poissoni, Megapora hyalinaj tliey are found together with a 

 stronglj' developed frontal cryptocyst. 



Acropetalous spines. Spines issuing from the circumference of a pore (pseudopore). 



Bilaminate spines. Spines (generally flat) the inner layer of which is formed by a 

 cryptocyst while the outer layer is formed by a gymnocyst. They are only found in the 

 family Catenariidae and reach their greatest development in the genus Costicella. 



Lateral chambers. Bryozoids generally developed as kenozooecia, found as a rule in 

 a number of four on each side of an internode in the family Catenariidae. 



Simple operculum. A well-chitinized or calcified separable operculum the hing-line of 

 which stretches between the two proximal corners and as a rule coincides with the 

 proximal edge of the aperture. 



Compound operculum. A well-chitinized separable operculum, the hinge-line of which 

 is placed distally to the proximal edge. Only the distal part of it corresponds to an oper- 

 cular valve or a simple operculum. In the Ascophora the proximal part of it, the »accesso- 

 rial part((, serves as' operculum to the compensation-sac. 



Peristome. A calcareous projection more or less completely surrounding the aper- 

 ture of the zooecium. The entrance to this, often tubular, projection is the ))secondary 

 aperture*. 



Ooecium (:= ovicell). A more or less calcified marsupium placed near the zocecial 

 aperture, into which the eggs pass from the zooecium in order to be developed into 

 larvae. 



Endozooecial ocecia. Internal ocecia consisting of an endoooecium formed by the distal 

 wall and of an ectoocecium formed by the covering membrane. 



Hyperstomial ocBcia. External two-layered ocecia, consisting of an endoooecium and a 

 more or less developed ectoooecium. 



Peristomial ooecia. Single-layered ocecia formed by the peristome. They are found in 

 the families Tubucellariidae and Lekythoporidae and perhaps also the ooecia of the families 

 Conescharellinidae and Holoporellidae may be referred to this division. 



Endotoichal ooecia. Hollows formed by resorption in a thick calcareous frontal wall 

 and at last opening outwards. They are found in the families Cellular ridae, Membranicella- 

 riidae and Setosellidae. ♦ 



Acanthostegous ocecia. Marsupial spaces lying between the covering membrane and 

 two series of concurrent spines. They are found in Electra zostericola and El. (Heteroceciam) 

 amplectens. 



Double-valved ooecia. Ooecia consisting of two arched hollow valves (kenozooecia). 

 They are found in Algsidium parasiticam. 



Basal mark. A curve seen on the basal surface of a hyperstomial ooecium, circum- 

 scribing that part of the frontal wall of the zooecium, which takes part in the formation 

 of the endoooecium's basal wall. 



Basal. The surface with which an incrusting colony is fixed and the corresponding 

 surface in a freely growing colony. 



Frontal. The surface opposite ,to the basal and that in which as a rule the aperture 

 is placed. Sometimes, however, the aperture may be terminal, viz., placed in the tip of the 

 zooecium. 



