72 Mr. H. J. Carter on the close Relationship of 



like that of ParJceria, &c., but massive, white, and opaque like 

 that of Ihjclmctina j^liocena, in the midst of which the tubes, 

 together with traces of the stclliform systems, show themselves 

 in dark lines filled with transparent calcspar, which, with 

 those of the undulating lamination indicated by broken lines 

 of circular holes and oblong spaces, are altogether so like that 

 of H. pliocoia, that the two, mutatis mutandisy are almost iden- 

 tical ; that is, the tubes are a little less in diameter trans- 

 versely, and there are traces of the stellate systems, which do 

 not exist in H.jylioccna. There are also lines of opaque white 

 matter across tlie transparent calcspar of the tubes, which 

 indicate here and there in their parietcs the presence of dia- 

 phragms and apertures, the latter indicating the union of the 

 tubes by intertubular channels like that represented in fig. 21, 

 to which I have before alluded as a feature of Syringopora. 



I have said " traces of stellates ;" but if the section had 

 been made horizontally or tangentially to the lamination, the 

 stellates would have been complete. This shows that to fairly 

 describe species of Stromatoptora it will be necessary to get 

 their natural surface as well as their interior, if possible, and 

 to cut the specimens vertically and parallel to the planes of 

 growth respectively, thus obtaining two surfaces, which will 

 then satisfactorily show the form, size, and relative position of 

 the elementary parts of the stmcture ; after which oblique 

 sections maybe made for further elucidation. All this I must 

 leave to my friend Mr. Sollas, who has paid much more atten- 

 tion to the subject than I have, and whose intention now is to 

 publish an exhaustive account of the Stromatoporoi as soon as 

 time peiTQits ; hence the brevity of my remarks. 



Meanwhile, to return to the calcareous specimen from the 

 Devonian Limestone, which Mr. Sollas presented to me as an 

 instance of hexactinellid structure closely resembling that of the 

 hexactinellid sponges, and which at the time I myself could 

 conceive to be nothing else, — I now find by actual comparison 

 that in stnicture it is almost too persistently regular for that 

 of any solid hexactinellid sponge with which I am acquainted. 

 In this specimen or species the vertical, which are the largest 

 white lines or fibres seen in the vertical section, are almost 

 continuous for a long distance, which is not the case in the 

 hexactinellid sponge-structure, and only has its direct type in 

 the structure of Tuhipora musica, where the interior of the 

 vertical tubes, as I have before stated, is inten-upted by dia- 

 phragms, and therefore not continuous, as might appear from 

 mere external examination ; while the horizontal fibres, which 

 are smaller, are equally continuous and hollow. Again, tui*ning 

 to the horizontal section (that is^ parallel with the lamination). 



