ORDER II 



CALCISPONGIAE— SYCONES 



71 



cloaca. Skeleton constituted of short, bluiit, and bent uniaxial, and also of 

 three- and four-rayed spicules. Triassic and Jurassic. 



Holcospongia Hinde. Jurassic and Cretaceous. Sestromostella Zittel. Trias 

 to Cretaceous. Synopella Zittel. Cretaceous. Oculospongia (Fig. 89) and 

 Diplostoma From. Cretaceous. 



Elasmostoma From. (Fig. 91). Foliate-, ear-, or funnel-shaped. Upper {i.e. 

 inner) surface covered with smooth dermal layer, in which large shallow oscula 

 are situated ; under surface cribriform. Cretaceous. 



Bhaphidonema Hinde (Fig. 92). Beaker-, funnel-, or twisted leaf-shaped. 

 Inner or upper surface smooth, with very small oscula or pores. Outer surface 

 rough, cribriform. Canal-system indistinct. Trias, Jurassic, Cretaceous. 



Pachytylodia Zitt. Funnel-shaped, thick-walled ; base with smooth dermal 

 layer; oscula present here, but absent on other parts of the exterior. Skeleton 

 composed of very coarse, anastomosing fibres. Cretaceous. P. infmidihulifm'mis 

 (Goldfuss). 



Order 2. SYCONES Haeckel. 



Walls traversed hy simple canals disposed radially with reference to the cloaca 

 and opening into it. Skeletal elements very regulaiiy arranged. 



Mostly small delicate forms inhabiting shallow water. 



Protosycon Zitt., from the Upper Jurassic of Streitberg, is a small, cylin- 

 drical, or conical form agreeing with living Sycons in the arrangement of its 

 radial canals. 



To the Sycons, Rauff assigns also the calcareous sponge Sphinctozoa described 

 by Steinmann (Jahrb. f. Mine- a 



ralog. 1882, IL p. 139), which is 

 distinguished from all other 

 Calcisponges by having a most 

 remarkable segmentation, such 

 as occurs in the Lithistid genus 

 Casearia. 



The oldest Sycons are 

 Sollasia, Amhlysiphonella and 

 Sebargasia Steinm., from the 

 Carboniferous Limestone of 

 Asturias. In the Triassic of 

 St. Cassian and Seelandalp, 

 near Schluderbach in Tyrol, 

 are found Colospongia Laube, 

 Thaimastocoelia and Cryptocoelia Steinmann. Thalamopora Roemer and Barroisia 

 Steinm., occur in the Lower and Middle Cretaceous. 



Barroisia (Fentriculites Zitt. non Defr. ; Sphaerocoelia Steinm.) (Fig. 93). 

 Occurs sometimes as simple, cylindrical, or clavate individuals, and again in 

 the form of bushy Stocks. Outer surface frequently constricted, summit 

 arched, with osculum in the centre, cloaca tubiform. The cylindrical indi- 

 viduals are composed of thin-walled, hemispherical, or compressed segments, 

 which are so arranged that the roof of one segment serves also as the floor of 

 the next following. The wall is every where perforated by simple radial canals, 



Fig. 93. 



Barroisia anastomans (Mantell). Aptian ; Farringdon, Berk- 

 shire. A, ßush-like colony, one branch sliced open ; natural 

 size. B, Individual cut through obliquely, 5/2 ; a, Junction of 

 two Segments ; 6, Cloaca ; 0, Osculum ; d, Radial canals. C, D, 

 Three-rayed skeletal spicules, 3«/i and 72/i (after Steinmann). 



