802 W. J. SOLLAS ON THE STRUCTURE AND 



spongia * (Siphonia excavata, Goldf.), which occurs in the Silurian, is 

 retained as a member of the family. 



The species described are S. ficus, Kosnigii, tuber osa (Scyphia tube- 

 rosa, Homer, 1840), ornata, astroides ; the last two of which are new, 

 while /$. tuberosa (as before mentioned p. 799) is a true Hexactincllid, 

 and has no place with the Siphonia?. 



S. pyriformis and 8. punctata are referred to Jerea ; and many 

 other species of previous authors find their place amidst new and 

 strange relationships, going into various other genera and even 

 different families. The new arrangements proposed by this re- 

 former are indeed bewildering, and help to show what, unfortu- 

 nately, is only too sufficiently obvious, the utter and distracting 

 confusion in which the classification of the fossil sponges is involved, 

 and which must continue without any prospect of order or finality 

 till the ultimate structure of the forms described is made the basis 

 of their arrangement, as in the case of recent sponges. 



The multiplication of synonyms which has grown up in conse- 

 quence of all absence of a guiding principle in the grouping of forms 

 will be seen in the appended Tables (pp. 825-833), the value of 

 which would be greater but for the fact that even the ordinal 

 characters of a great number of the species which are therein 

 named are unknown, and cannot be discovered from an examina- 

 tion either of the figures or the descriptions of their authors. 



1866. D'Eichwald, E. ' Letlwea Rossica,' vol. i. p. 329 ; vol. ii. sec. 

 1, pp. 100-102. 



In vol. i. p. 329, a new species, Siphon! a cylindrica (Eichw. non 

 Reuss), is described from the Orthoceratite bed of Zarskoje near St. 

 Petersburg. There are no characters about this sufficiently marked 

 for its reference to the sponges at all, and certainly none to show 

 that it is a Siphonia. Siphonia prcemorsa and excavata, Goldf., are 

 given from the same horizon at Zarskoje, Poulkowa, and various 

 other localities. 



In vol. ii. p. 100, we find a description of the genus Siphonia, 

 which is said, partly on the evidence of the species cited in vol. i., 

 to range from the Palaeozoic into the Mesozoic periods, attaining its 

 maximum in the Cretaceous. 



Two new species, S. pirum (pi. vi. fig. 8), a doubtful member of 

 the genus, and S. rivuligera (pi. vi. fig. 7), a large and symmetrical 

 form very similar to S. pyriformis, Sowerby, are described and figured 

 from the Neocomian ; and S. radiata of Fischer is mentioned as 

 occurring in the Cretaceous of Bouschevoyc, near Moscow. 



1868. Bowerbank, Dr. J. S. " A Monograph on the Siliceo-fibrous 

 Sponges," pt. ii. (Proceedings of the Zoological Society, 1869, 

 p. 342, pi. xxv. figs. 6 & 7). 



Dr. Bowerbank gives the name " Pur'isiphonia " to a new genus of 



* Zittel shows that this sponge is a true Hexactinellid (Abhandlungen der 

 k. bayer. Akademie der Wiss, ii. CI. xiii. Bd. i. Abth. pp. 35 & 44). 



