M. K. A. Zittel o/i Fossil IlexactinelUda. 515 



"which reach only to the inner wide-meslied layer. On the 

 inner wall the mesh-openings serve as influent ostia. 



^Sci/phia heteromorpha, Reuss, Bohm. Kr. xviii. 1, 2 

 (non 3, 4). 



Family 9. CceloptycMdae. 



CcELOPTYCHiUM, Goldf., see p. 419. 



Cceloptychmm agaricoides, Goldf., Zitt. Abhandl. k. bayr. 



Akad. ii. CI. Bd. xii. iii. p. 59. 

 C. deciminum, Rom., Zitt. ibid. p. 62. 

 C. lobatum, Goldf., Zitt. ibid. p. 73. 



B. Lyssakina, Zitt. |. 



ACANTHOSPONGIA, M'Coy. 



Syn. Sil. Foss. Ii'el. p. 67 (Acanthasponffin) . 



The great axis of the spicules becomes 5-10 millims. long, 

 the other two are shorter. The crossing-nodes are thickened 

 and solid. The six arms become thinner towards the tip, and 

 swell towards the centre. Axial canals distinctly visible. 



'\Acanthospongia silurensis^ M'Coy, I. c. p. 67. 

 A. Sinithu, Young, Nature, 1876, p. 481. 



Stauractinella, Zitt. 



Form of the sponge-body spherical, unstalked. Skeleton 

 consisting of large, simple, isolated sexradiates with arms of 

 unequal length. In general one ray is much elongated (6-8 

 millims. long). The spot at which the arms cross is scarcely 

 thickened ; and generally the arms are of the same thickness 

 throughout their whole length. 



Stauractinella jurassica^ Zitt. 



? ACESTRA, F. Rom. 



Fossile Fauna der Geschiebe von Sadewitz, p. 56, t. vji. 7. 



The bacilliform bodies are possibly spicules from the root- 

 tuft of a Hexactinellid. 



Supplement. 



The foregoing Memoir was read on the 13th of January 



\ Possibly the genus Astraosptmgia, Rom., is also to be referred as an 

 aberrant form to tlie Lyssakina, although tlie large stellate spicules, con- 

 sisting of calcspar, of this sponge possess three axes lying in the same 

 piano and besides these a perpendicular (but always ruiliinentarv) axis. 



35* 



