510 M. K. A. Zittel on Fossil HexactinelUda. 



gasti-al cavities. Outer (/. e. lower) surface constituted as 

 in Tremadictyon. Latticed skeleton rather irregular, the 

 siliceous ti-abeculfe often thickened or lamellarlj dilated. Cross- 

 ing-nodes imperforate. The ostia of the radial canals lie on 

 the outer wall ; the canals pass obliquely through the wall, 

 then run on for a certain distance below the inner surface, and 

 open in the oscuia of the upper surface. Both surfaces veiled 

 by a covering layer consisting of cross-spicules of moderate 

 size cemented together. 



Spongites hcliensis^ Quenst. Jura, Taf. 89. 96. ( = Scyphia 

 Buchi^ Goldf. xxxii. 8.) 



POKOCYPELLIA, Pomel (emend. Zitt.). 



Paleont. de I'Oran, p. 77. 



Top- or pear-shaped, small, thick-walled, attached by the 

 pointed lower extremity. Central cavity tubular ; its wall 

 with round ostia of simple straight radial canals arranged in 

 longitudinal rows. Latticed skeleton irregular, with octahe- 

 dral crossing-nodes ; the lateral apertures of the hollow octa- 

 hedra are small and usually unequal, often somewhat distorted. 

 Surface and upper margin coated with a smooth siliceous 

 membrane perforated by large round pores ; in this the axes 

 of large sexradiates are imbedded. 



'^ Scyphia pyriformis, Goldf. iii. 9. 



Caseaeia, Quenst. 

 Jura, p. 681. 

 Cylindrical or cup-shaped, pointed below, divided by nume- 

 rous constrictions into annular segments. Central cavity 

 tubular. Surface coated w4th a very regular latticed web, 

 consisting of normally coalescent sexradiates with broad and 

 short arms, in which the outwardly directed arm is always 

 aborted. This covering layer penetrates iiito the wall at the 

 places of constriction, and forms convex floors, by which the 

 individual segments are separated from each other. The ostia 

 of the straight radial canals are veiled both outside and inside 

 by the covering layer. The true latticed skeleton of the wall 

 is remarkably irregular, the coalescent sexradiates grouping 

 themselves without any order around the canals, and, moreover, 

 often possessing lamellarly dilated and distorted arms, in which 

 independent axial crosses are situated. The crossing-nodes 

 are imperforate. 



^Scyphia articulata, Goldf. iii. 8. 

 Casearia eurygaster^ Zitt. 



