Heviews — Dr. Rmif^s PalcBOspongiology. 467 



noticed in the Geological Magazine.^ The present issue begins 

 the special portions of the work which treats of" the characters and 

 relations of the different genera and species, taking them in the 

 order of their geological appearance. In these two parts the sponges 

 from the Cambrian rocks, and a considerable number of those from 

 the Silurian, are described in great detail, and in most cases both 

 the sponges themselves and their minute and often intricate skeletal 

 structures are figured either in the text or in the beautifully-executed 

 plates, with striking fidelity. The majority of the forms are not 

 new to science, but it may be said of many of them, hitherto only 

 superficially described, that their characters are now made known 

 for the first time. In several respects the sponges from the older 

 rocks present greater difficulties to the student than those from the 

 Mesozoic formations, for they are often less perfectly preserved, 

 and the structures in some differ markedly from those of a later 

 age ; but these obstacles have been successfully overcome by the 

 author, who has worked out the construction of their skeletons 

 with much skill and patience. 



From Cambrian strata but a small number of species are known, 

 and these as a rule only by imperfect fragments. The Hexactinellid 

 genus Protospongia is the most widely distributed form, but it is 

 principally represented by detached spicules and small fragments 

 of the mesh, which, as regards preservation, fall far short of those 

 discovered by Dawson in the Ordovician strata of Metis. Lithistid 

 sponges from the Upper Cambrian of the Mingan Islands are better 

 preserved, at all events in the case of the remarkable Archmoscypliia 

 Minganensis, Bill., sp., whose affinities to this group, which had been 

 disputed by Bornemann, are confirmed by the author ; another form, 

 first described by Billings, is the Nipterella paradoxica. Dr. Rauff 

 very properly excludes from the group a number of peculiar bodies 

 from the Cambrian of New Brunswick, which Mr. G. F. Matthew 

 had placed under sponges, apparently because they would not fit in 

 with any other class of organisms, and also the doubtful Leptomitus 

 Zitteli, Walcott, and a few others. 



Coming now to the Silurian (in which the Ordovician is included 

 by the author), we meet with a very considerable increase in genera 

 and species both of Hexactinellid and Lithistid sponges. The Hexac- 

 tinellids all belong to the Lyssakine division, and are referred to 

 the following genera: Protospongia, Dictyophytra (=iDictyophyton, 

 Hall), Cyathophycus, Palceosaccus, Acanthodictya, Plectoderma, and 

 Teganiwn, n.g. 



An interesting new form of this group, from the Wenlock Lime- 

 stone of Dudley, is described under the name Oncosella catinum, n.g. 

 et sp. Only one specimen of it is as yet known, and it is remark- 

 able to find that it retains its form fairly complete and uncompressed, 

 although its original siliceous skeleton has been altogether replaced 

 by calcite. Yet other Hexactinellid genera of somewhat less regular 

 build are Pattersohia, Miller (=zStrobilospongia, Beecher), Brachio- 

 spongia, and Amphispongia. Dr. Eauff does not hesitate to rank this 

 1 Dec. III. Vol. X. 1893, p. 524. 



