335 



sutures. The aperture of the gonozooecia is considerably larger and broader than 

 that of the ordinary zooecia. 



The avicularia occur extremely rarely and most frequently singly in the dis- 

 tal corners of the zooecia, but on the gonozorecia there is not rarely one on each 

 side. They are concave, of a more or less regular, elongated oval form, and the 

 opercular area, which is separated from the subopercular by an arched trans- 

 verse ridge, is provided with a well-developed cryptocyst. The mandible points 

 directly or obliquely proximally. 



Of this species, which appears in free, two-layered plates, I have examined a 

 dry fragment from Victoria (Miss Jellj'). 



Cyclicopora Hincks. 



No spines and no distal arch. The zooecia have scattered pores and the cir- 

 cular aperture, which has no hinge-teeth, is provided with a slightly chitinized 

 operculum. No avicularia. The oa>cia consist of a membranous ectoooecium and 

 a calcified endoooecium provided with scattered pores. Multiporous rosette-plates. 



The genus, which only comprises a single species C. praelonga Mac Gill. 

 (C. lon(jipora Hincks), is referred by Hincks to a separate family Cijclicoporidae, 

 which is based in general on the simple structure of this form and not on def- 

 inite positive characters. The most important, systematic character is shown in 

 the ooecia, which agree essentially with the corresponding structures in the family 

 Escharellidae, consisting of a membranous ectoott'cium and a calcified endooa-cium. 

 They differ however from all other ooecia in this family, in that their basal 

 wall is formed in the whole of its extent by a portion of the frontal wall of the 

 distal zooecium, whilst this only partially occurs in such genera as Escharella 

 and Escharoides. This genus is therefore provisionally and with great doubt 

 referred to the Escharellidae. 



Family Smittinidae. 



The zooecia are seldom provided with 1 — 8 spines. A vestibular arch is wanting 

 or weakly developed. The avicularia are rarely lateral and a median, symmetric- 

 ally or asymmetrically placed avicularium appears most frequently. The owcia 

 have as a rule a calcified, very rarely a membranous ectoooecium which is usu- 

 ally provided with pores. Rosette-plates with one or several pores, more rarely 

 pore-chambers. 



The two families Smittinidae and Escluirellidae are not sharply distinguished, 

 and a comparison of the characteristics of the two families shows that the char- 

 acters taken singly may appear in both families, though to a very different ex- 



