436 Geological Society. 



The genus Ischadites consists of conical or ovate bodies enclosing 

 a central cloacal cavity -with a summit-aperture. The basal nucleus 

 or commencement of growth consists of eight small spicules arranged 

 in a circle ; the spicule-plates are rhomboidal ; there is no inner 

 plate, as in ReceptaculUes. The genus Tetmgonis, Eichw., is un- 

 doubtedly congeneric with L-chadites, and, being of later date, be- 

 comes obsolete. Acanflioclionia,g.n.,Tes(:m.hles Ischadites in spicular 

 structure, but it is open cup-shaped; it is formed to include a single 

 species, named A. Barrandei, from Bubowitz, in Bohemia. The genus 

 Sphcprospoiujia, Pengelly(pars Salter), has hexagonal summit-plates, 

 and the vertical spicular rays are only partially developed. The 

 genus BeceptacuUtes is cup-shaped ; the spicular plates are rhom- 

 boidal, and the vertical rays develop at their extremities definite 

 plates,, which apparently amalgamate into a continuous perforated 

 layer. The author concluded that the Keceptaculitidse constitute 

 a distinct family of siliceous hexactiuellid sponges, whose nearest 

 relationships are to Protosponyia, Dktyophyton, and Plcctoderma. 



The genera Ci/docrinus, Eichw. ( = I\idHlites, Salter), Fasceolus, 

 Billings, and Archceoci/athus, Bill., though ranged with the Becep- 

 taculitida3 by some authors, were shown to have no structural rela- 

 tionship to that family. 



8. " On the Pliocene Mammalian Eauna of the Yal d'Arno." 

 By Dr. C. J. Eorsyth Major. Communicated by Prof. W. Boyd 

 Dawkins, E.E.S., F.G.S. 



A list of the fossil Mammalia was given, containing the names of 

 thirty-nine species known to the author. This list contains no 

 species common to the older fauna on the limit between Miocene 

 and Pliocene, a fauna characterized by the presence of Hippxirion 

 and met with at Pikermi, Eppelsheim, and other places. The 

 Montpcllier fauna contains an admixture of older and newer types ; 

 but it is not clear that this admixture has not taken place after 

 extraction. Some Yal d'Arno types extend to the Sewaliks of 

 Northern India, for Equus Sti7ionis and Svs Strozzii of the former 

 are probably the same as E. sivalensis and Siis giganteus of the 

 latter. 



It has been asserted that the marine Pliocene of Italy is older 

 than the lacustrine strata of the Arno vallc}-. This, however, is 

 not the case ; some of the mammalian species found in the latter 

 occur also in shore-deposits belonging to the first named. 



The Pleistocene fauna in Italy appears to be quite distinct speci- 

 fically from the Pliocene. Portions of both, however (often desig- 

 nated the African division), appear to be closely allied. This is 

 especially the case with certain forms of Hycma, Felis, Rhinoceros, 

 and Hippopotamus. Some of the differences between species of the 

 two last-named genera were discussed. 



The relations of the Arno-vallcy fauna to living Mammalia were 

 next considered, and it was shown that although some genera, as 

 Hippopotamus, are only met with living in the Ethiopian region, a 

 much larger number of forms, such as Tapirus and several bovine and 



