13 



on the surface by small apertures, un<J JO-MULT more or less vertically through the component 

 layers of the muss (/W. /'".<.., p. 14 and p. i '..">). There is some ambiguity in the language 

 used by this eminent palaeontologist in deseribing the-e tubes and their openings in ,S. con- 

 renfri'-'i ; and the evidenee is nut at jiresent sufficient to warrant any po-itr. :aent of 



opinion as to whether they may correspond with the "pores'" or the oscula " of an ordi- 

 nary sponge. It is probable, however, that they should be regarded as rej.re-,.-nting th< 

 "pores," and that the' - osculu" will yet be discovered by a more extended and careful ex- 

 amination. Again, in S. ostiltt'i, (Nieh. ), a species from the (iuclph formation of Canada, the 

 upper surface of the mass carries .-mall but regularly arranged njiening-. wliieli can hardly be 

 regarded as being other thr.n o-cula'' (Annuls "/ ' ^'adirnl ///W///, A g . 1-7:;. p. i<n, I'l. 4, 

 fig. 1). In ,v. iiih.j-i-iilntn (Nich. |, again, I have now discovered a -y-t. in of comj.aratively 

 large, though remote, openings which communicate with canals traversing the organism, and 

 which appear to fulfil beyond all question the function of exhalant apertures, Undoubted 

 oscula also occur in S. i/ru//.ii'(t<'. La.-tly, in the >'. / rf<mi.tn (Nich.), now described for the tir.-i 

 time, the entire mass is perforated by numerous and close-set canals, of considerable size, open- 

 ing at the surface in rounded apertures and generally at the summit of chimney-like or coni 

 cal eminences. These opening.- must represent "oscula." It is true that in few instances 

 with which I am acquainted has any species of Strut/in tnpt-irn been shown with certainty to 

 possess two sets of apertures, small and large, one set being inhalant and the other exhalant. 

 It must be remembered, however, that the difficulties of observation in thisca-e are very great 

 and the " pores " might have escaped notice either from their minute size, or from the condi- 

 tion of mineralisation in which the-e t'.--ils occur, all the cavities of the ma.-s being tilled up 

 with foreign matter, and the reticulated tissue itself being often silicified. Or, it is possible 

 that in some of these ancient forms the two sets of apertures were of equal size, and are thus 

 incapable of being distinguished in a fossil condition. Still there are some . which 



fossUs in other respects ret'.-rable to XtniiiHifopora have been shown t> - both inhalant 



and exhalant apertures. The eases in question are $. <n'>niuLi(>i iNielij. in a singles] 

 men only ; N. /////>//<'/if (Ni.-li. a -till undeserilied species from the Niagara lime.-tone of 

 Indiana, and .v ///','/./ (Nieh.j, from the Niagara limestone of Canada. Of this la>t named 

 species, I append an engraving in which these two sets of apertures are well exhibited. 



,-. The -liajie ot'tlie various .-; 



i- -u.'h a- \vould aeeord 

 etly well with the beliet'that that 

 are Sj...iu Some are in tin 1 



form of rounded or irregularly hemi 

 sjiherieal nr < itlp-r- 



uwliat euji shaped ; an '. 

 again, liave the lorm of irregular 



ided eru-t-. apparently attached at 



one point to -nine - lid l>dv, from 

 whieli th.-y sj.ivud laterally in every 



direction. 



I'j.on the \vliole 1 think the ovi 

 d. nee is very deeidedly in favour of 

 the \ ie\v thai the g.-mi 



Me to (lie i ( h 



rdanee with tlii- view, | -i, all retain 



ill Mli- ' enil- tile fi.rilis here d- 



v 



,7 



'./// ami >'. lino* 



tli.'-e. -it any rate, aj.j.e.ir (.. be un 

 qiie-ti. .iia)> , iiid ill- '. 



i an\ I'llier \ i, w ..I the atlinil : 

 . : 



. !i, In- funned f. if the: ! i.' 



V 1 '' 1 ' ''iT-- r 'I he eeoui 



N i.i u.i lin . . . 



have commenced i tonec m the 



Lower SUmriao and to h*Te died oui in the c.-irloniier..;i- j.. ri-d In tlie DevoDiao 



the geniU WOuId -in t> ha\> ait lined il- maximum ; and 1 have t.. ne.'iil QQ 



