68 M. K. A. Zittel on Fossil Calcispongiaz. 



allied forms by the narrow tubular central cavity of the cylin- 

 drical body and by the absence of any radial canals. The 

 forms belonging to it were named by the older writers Scy- 

 phia, Spongia, or Siplwnia ; D'Orbigny erroneously united 

 them with Lamouroux's genera Eudea and Hippalimus, 



Etallon (Etudes pal. sur le Haut-Jura, 1859, p. 142) pro- 

 posed for a part of the species described by D'Orbigny as 

 Eudea and Hippalimus the generic name Pareudea 1 under 

 which are included the Jurassic forms of the present genus, as 

 well as several Eusiphonellw. 



In the same year Fromentel (Introd. p. 31) established the 

 genera Siphonocoelia and Polycoelia, which, in general, repre- 

 sent Etallon's Pareudea. The monozoic forms were named 

 Sipihonoccelice, the polyzoic Polycoelice, and, as the latter name 

 was already occupied, subsequently Discoelice (Cat. rais. Spon- 

 git. Neoc. 1861, p. 4). This correction has escaped most 

 authors ; and the name Polycoelia was therefore replaced by 

 Dendrocozlia by Laube, by Cceloscyphia* by ft. Tate, and by 

 Plioccelia by Pomel. 



A generic separation of the monozoic and polyzoic forms is 

 quite inadmissible in this genus ; for sometimes the same 

 species makes its appearance as a simple individual and as a 

 composite stock. Nor does the genus Stenocoelia, From. 

 (Cat. rais. p. 4) seem to me to be any better founded. Fro- 

 mentel refers to it those Disccdiai in which the individuals are 

 fused together laterally almost to the vertex, so that nodular 

 stocks with perforated wart-like elevations are produced. 



In his most recent work Quenstedt describes the Jurassic 

 forms under the generic denominations Spongites, Vermi- 

 spongia, and Radicispongia, and the Cretaceous ones gene- 

 rally as Scyphice. 



The above-cited genera of Pomel are distinguished partly 

 by the supposed siliceous or calcareous nature of the skeleton, 

 partly by the thickness of the anastomosing fibres, and partly 

 by the external form. 



It appears to me not improbable that when we have a 

 better knowledge of the spicules which compose the skeletal 

 fibres, a division of the forms united under Peronella into 

 several genera may be practicable ; for that in this respect 

 very important differences occur, may be seen at once from a 

 comparison of the spicules of Peronella cylindrica from the 

 Upper Jurassic, and of P. multidigitata, Mich., from the 



* Judging from the figure of Cceloscyphia sulcata, Tate (Quart. Journ. 

 Geol. Soc. xxi. p. 43), I suppose that this species does not belong to the 

 Calcispongiae, but to the Hexactinellidse, and, indeed, in the neighbour- 

 hood of Potyblastidium, Zitt. 



