M. K. A. Zittel on Fossil TAtMstidcv. 333 



Miocene of Oran, of which only the external form is known. 

 Here also probably 



Plococonia, Pom. 

 (Pal. d. rOran, p. 248.) 

 Spongia, Plocoscyphin p. p., auct. 



Sponge consisting of mgeandrically contorted thick lamellfe, 

 stalked. Skeleton ? 



1. Spongia contorto-lohata^ Mich. Ic. xlii. 1. Senonian, 

 Tours. 



Seliscothon, Zitt. 

 Scyphia, Goldf. 

 Spongia, Phill. 



Chenendopora p.p., Cupulospongia p.p., and Ocellaria p.p., Rom. 

 Trachydictya and Laosciadia, Pom. 



Sponge plate-, basin-, funnel-, or cup- shaped, stalked. 

 Upper margin thick, rounded, or obliquely truncate. Wall 

 composed of thin, radial, perpendicular lamellas, separated by 

 fissure-like spaces of the same breadth, which replace the 

 canal-system. Upper (inner) surface with shallow round 

 ostia, sometimes also with numerous pores. Under (outer) 

 surface smooth, or clothed with a dense siliceous membrane. 

 The ostia of the upper surface open directly into the radial 

 fissures. 



Skeleton composed of fine, irregularly branched, siliceous 

 corpuscles, covered with spinous or root-like processes, and 

 forked at the ends of the main branches. These corpuscles 

 are close together in the vertical lamellfe, and intimately inter- 

 woven by their processes ; and some of them project into the ver- 

 tical canals, and attach themselves by their ends to the neigh- 

 bouring lamellas, forming, as it were, bridges (see Goldf. Ixv. 

 5 J). At the surface the corpuscles are rather more strongly 

 branched, and form a finely porous covering-layer, in which 

 numerous baeillar spicules, pointed at both ends, arc scattered. 



This genus differs from Chonella by the radial lamella3 

 forming the wall, and by the absence of special canals. 

 Sometimes the lamellar structure of the wall is less distinct, 

 the lamellge are bent and more frequently united by bridges, 

 so as to produce forms difficult to classify, and constituting an 

 almost insensible gradation to Chonella. 



Pomel proposes two genera for these sponges : — Laosciadia 

 for those furnished with distinct ostia, such as S.j^lana, Phill.; 

 and Trachydictya for the species with a finely porous surface, 

 like 8. Mantelli. The latter genus is placed by Pomel with 

 the Hexactinellidse. 



