396 SUMMARY OF CUEKENT RESEARCHES RELATING TO 



The author recommends the study of the form and development of 

 the embryonic parts of the skeleton as affording the best criterion of 

 the correctness or want of correctness of the alliances here suggested. 



Fossil Sponges in the British Museum.* — This fine work from 

 the pen of Dr. G. J. Hinde, a pupil of Prof. Zittel, the great leader in 

 the modern development of the palaeontology of sponges, is a fitting 

 tribute to the excellence of the principles of classification which 

 have been laid down by the distinguished professor. Its classification 

 is based essentially on the principle of the employment of the 

 minute structure of the skeleton for its fundamental distinctions. 

 While the adoption (in the Introduction) of the older, Hiickelian, 

 grouping of the tissues of living sponges into syncytium (ectoderm 

 and mesoderm of Schulze) and ciliated cells (entoderm of Schulze) is 

 not a happy feature, yet, on his own ground, Dr. Hinde does good 

 service in his careful account of the mineralogical characters of fossil 

 sponges. He upholds the ready replacement of organic silica by calcite. 

 Diagnoses are given of the British species and the new foreign ones ; 

 references are given in the case of the remaining described species 

 from foreign horizons ; the rich collections of William Smith, 

 Toulmin Smith, Mantell, and Bowerbank render the British part of 

 the collection particularly interesting, and the work may be regarded 

 as a manual of British fossil spongology. 



The new genera are 27 in number ; of these, Climacospongia, 

 Lasiodadia, and Acanthorhaphis are siliceous Monactinellids ; the first 

 strongly resembles Seniera in the recent series. AcantJiorJiapJiis is 

 perhaps related to the recent Metschnihowia of the Caspian Sea. The 

 Lithistidfe, as might have been anticipated, contribute largely to the 

 long list of new types, viz. 10 genera. Of these, the Megamorina are 

 represented by Placonella, Holodictyon, Pachypoterion, Nematinion, 

 chiefly distinguished by general form or by points in the arrangement 

 of the internal " canals." To the Tetracladine group of Lithistids 

 Dr. Hinde adds no less than six new types, viz. Bolospongia, Kalpinella, 

 Thamnospongia, Pholidocladia, Phymaplectia, Bliopalospongia ; in the 

 last alone does any considerable divergence from the normal character 

 of Tetracladin8e appear in the spiculation, viz. a part of it inclines 

 towards the Ehizomorine type. It is noteworthy as illustrating the 

 advance made by the new system of classification, that a close 

 resemblance is to be traced between the external form of some of 

 these genera and that of genera belonging to quite different groups. 



Considering its wider range in time and its greater comprehensive- 

 ness, the order Hexactinellida is not so richly represented by new 

 types in this collection as the Lithistidse. Among the forms with a 

 continuous skeleton (Dictyonina), the Euretidse contribute two such 

 types, viz. StrepMnia, which forms irregular or cup- shaped expan- 

 sions — a habit unusual in the recent members of this family, and 

 Sestrodictyon. Ventriculitidae are represented by a new form, Sestro- 



* ' Catalogue of the Fossil Sponges, in the Geological Department, &c.., 

 with descriptions of new and little known species.' 4to, London, 1883, 248 pp. 

 (38 pis.). 



