301 



inserted between the membranous eclooa^cium and the calcified endoooecium. 

 From Waters' statement^ regarding tliis ort'cium : »I propose to call this a con- 

 cealed ovicell, retaining the expression immersed for those which give an external 

 indication of their presences one would conclude that the oa'cia in the specimen 

 examined by Waters were not distinctly seen on the surface of the colony. 



Avicularia. The peristomial arch is on each side provided with a large, robust, 

 triangular, obliquely ascending avicularium, and the broad, trapeziform proximal 

 part of the mandible grades over into an elongated part, the two, almost parallel 

 lateral edges of which finally run together in a stout terminal hook. 



Of Ibis species I have examined several colonies with labyrinthine-like branch- 

 ings and round or compressed, two-layered branches from the Cape and Port 

 Elizabeth. 



To the genus Mijriozoiim belong the species M. tniiiccitiini, M. coarcliiliini, M. siib- 

 gracile and probably also the species described by Busk," M. hoiioliilense, M. 

 simplex and M. marionense, in the last of which the oa'cial cover only reaches 

 halfway down over the frontal surface of the oa'ciuni. To this genus I must also 

 refer the two-layered, laminate 'Esclutroides-^ occliisa Busk^ and the one-layered 

 ySchizoporeUn« hitiirrita Hincks,^ which shows several points of agreement with 

 Geplujrojihont pohjmorpha. The genus Mijriozoella is only represented by a single 

 species, the incrusting M. cnislcicea Smitl. 



Family Sclerodomidae n. f 



The zou'cid, which have a covering membrane but no spines, are very thick- 

 walled and consist of a very solid and hard, finely striated calcareous mass, which 

 is perforated by pore-canals, sometimes scattered, sometimes arranged within the 

 lateral margins. The very small distal wall is provided with a number of uni- 

 porous rosette plates and the lateral walls with a varying number of rosette-plates 

 with few (2 — 3) pores. There is a membranous or weakly chitinized operculum 

 and a more or less well-developed peristome. Dependent (uncubtriii are present and 

 are frecpiently situated within or outside the peristome. The hyperstomial o<vcia, 

 which have a membranous ectooa>cium, are only distinct on the surface of the 

 colony in quite the youngest zowcla, as they are quickly covered over by a 

 thickened layer or by the peristome. The colonies are free, branched. 



Genera. 



The peristome is funnel-shaped, immersed, not projecting, provided 

 with avicularia; no peristomial pore; in the oo3cium-bearing zooccia 



• 110, p. 29 — .•!0, in. II, figs. 21—24. - 8. p. 1711. ' 110, p. 26. ^ 29, p. 280. 



