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



scarcely developed ; ostia very small, irregularly distributed. 

 Surface naked. Skeleton as in Sjporadopyle. Axial canals 

 of the sexradiates wide. 



'^Scyphia verrucosa^ Goldf. Taf. xxxviii. 8 a-d. 



S. gregaria, Quenst. Jura, Taf. 81. 80. 

 '^Polycodia laevigata^ F. A. Rom. Spongit. taf. xi. 8. 



Family 3. Coscinoporidse. 



? BoTHROCONis, Kingt. 

 Monogi'. of Permian Fossils, Pal. Soc. 1849, p. 14. 



Leptophragma, Zitt. 



Sponge-body cup-sliaped. Wall thin. Both surfaces with 

 numerous small ostia of very fine csecal radial canals, gene- 

 rally arranged in longitudinal and transverse rows. Skeleton 

 stony, consisting of a dense latticed tissue of rather irregular 

 arrangement. The meshes between the siliceous fibres are of 

 very various forms. Crossing-nodes of the sexradiates solid. 

 Structure of the root agreeing with that of the wall. 



^Scypliia Murcldsonii^ Goldf. Taf. Ixv. 8. 

 S. striatopunctata, Rom. Kr. 3. 7. 

 S. angularis, Rom. Kr. 3. 2. 

 S.JragiLis^ Rom. Kr. 3. 11. 



Pleurostoma, Rom (p. p.)- 



Nordd. Kr. p. .5. 



Sponge-body laminar and cup-shaped or branched, always 

 strongly compressed, with a series of large apertures on the 

 rounded narrow surfaces. Wall thin, on both sides with 

 numerous, irregularly arranged, small ostia. Radial canals 

 simple, blind. Skeletal structure as in the preceding genus. 



Pleurostoma radiatum, Rom. Kr. 1. 11 t- 

 P. hohemicumy Zitt., n. sp. 



Guettardia, Mich. 

 Iconogr. Zoophyt. p. 121. 

 Sponge-body stellately folded. The three to eight folds of 



t The position of this genus is very doubtful. According to the figure 

 (Perm. Foss. pi. ii. fig. 7 a) it appears to belong to the Hexactinellida. 

 StiU more problematical is Conis, Lon?d. (Quart. Journ. Geol. Soc. v. 

 pp. 55-Go), fi'om Athei-field, which possibly possessed a calcareous skele- 

 ton. 



X Pleurodoma lacunosum, Rom., belongs to the family Callodictyonidfe, 

 and is the typical species of the genus Pkiuope, 



