108 SILICEOUS SPONGES. 



the cases in which replacement by calcite has occurred, though, as a rule, they are 

 pretty clearly shown. Should further research prove that the nodes are compact, 

 this species will have to be formed into a new genus, which will find its place close 

 to VerrucocoeUa. 



Distribution. Upper Jura : Randen, Switzerland. 



I 



Trochobolus constrictus, Hinde, n. sp. (Plate XXV. figs. 4, 4 a, 4 b.) 



Sponge subcylindrical, surface uneven, with slight concentric swellings and depres- 

 sions, the summit truncate with rounded margins. Length of tlie only specimen 

 87 mm., width at summit 29 mm. 



The thickness of the sponge-wall, measuring from the interior of the cloaca to the 

 outer surface, is 5 mm. The outer surface exhibits a vertical series of ridges about 

 2 mm. in width and 1 mm. apart. The characters of the interior of the cloaca are 

 concealed by the matrix. The wall is built up of a regular spicular mesh with 

 lantern or octahedral nodes. The distance between the nodal centres is -312 mm. 



The general appearance of this sponge so closely resembles the cylindrical examples 

 oi SphenauJax {Scyphia) costata, Goldf., that, judging from this character merely, it 

 would at once have been placed under this species ; but in a longitudinal section of 

 the wall the spicules exhibit distinct lantern nodes, and are similar to, though some- 

 what larger than, those of T. crassicostus. 



Distribution. Upper Jura : Randen, Switzerland. 



Genus PHLYCT^NIUM, Zittel. 



Phltct^nium coniformis, Quenst. sp. 



1878. Mastospongia coniformis, Quenst. Petref. Bd. 5, p. 152, t. 122. f. 13. 

 1826-33. Sctjphia verrucosa, Goldf. p. p. Petref. 1 Th. p. 7, t. 2. f. 11. 

 1878. Phlycttenium coniformis, Zitt. Neues Jahrbuch, p. 61. 



Distribution. Upper Jura : Heuberg, Wiirtemberg. 



Genus VENTRICULTrES, Mantcll, 1822. 



Ventriculites radiatus, Mantell, pars. 

 1822. Ventriculites radiatus, Mantell, Foss. of tlie South Downs, p. 168, t. 10, 11, 12, 11, 



nou t. 13. f. 2-6. 

 1815. Alcyonium chomides, Mantell, Trans. Linn. Soc. vol. ii. p. 402. t. 27-30. 

 1845-46. Scyphia radiata, Reuss, Ver. boh. Kreide, p. 7-t, t. 17. f. 14. 

 1854. Ventriculites radiatus, Mantell, Medals of Creation, 2 ed. p. 244, f. 81. 

 1870. Retispongia radiata, Ferd. Roemer, pars, Geol. Oberschles. p. 302, t. 32, non t. 30. f. 5. 

 1878. Ventriculites radiatus discus, Quenst. pars, Petref. Bd. 5, p. 449, t. 136. f . 26. 



