Reviews — H. Rauff- — On Receptaculites. 519 



doubt, that the original mineral structure of Beceptaculites and its 

 allies must have been extremely liable to change, for in by far the 

 greater number of specimens, as already mentioned, it has either 

 been entirely removed or replaced by granular calcite, silica or other 

 substances, in very much the same way as we find the originally 

 siliceous skeletons of fossil sponges ; whilst in only two or three 

 specimens is the skeleton composed of this peculiarly arranged 

 fibrous calcite, believed to be its original structure. A very striking 

 exemplification of the difficulty of satisfactorily determining whether 

 this fibrous carbonate of lime is original, or secondary, is afforded by 

 the inability of Dr. Eauff to make out whether the fibrous structure 

 now occurring in the axial portion of the horizontal or tangential 

 arms of the spicules of Receptaculites, represents an originally solid 

 portion of the arm, or is merely secondary infilling of a canal or 

 cavity. These doubtful structures, spindles as they are termed, 

 prove very durable, and remain when the walls bounding them have 

 disappeared. Dr. Rauff is inclined to consider the spindles to have 

 been originally solid, but if one might judge from silicified specimens 

 they are probably secondary solid infillings of an original canal or 

 cavity in the arms. 



Dr. Rauff definitely accepts the calcareous nature of the Becepta- 

 culitida and concludes, in spite of the remarkable general resem- 

 blance of their spicules to those of siliceous JiexnctinelJids, that they 

 could have no relationship to sponges. At the same time he is 

 unable to find in them any resemblance or relationship to any other 

 group of fossil or recent organisms, and can therefore give no clue 

 to their probable position, although he thinks that the question of 

 their alliance to the calcareous Algee, such as the Siplwnece verticil- 

 latce, put forward by Steinmann, Deecke, and others, deserves further 

 consideration. 



As regards the general structure of Beceptaculites itself, Dr. Rauff' 

 adopts Billings' view that they were, when perfect, conical or sub- 

 spherical in form like Ischadites, and consequently that the cup or 

 platter-shaped examples, which are the only ones known up to the 

 present, are incomplete. Theoretically there is much to favour this 

 view, more particularly as in no specimen yet discovered are the 

 margins of the open cups perfect, but on the other hand it is very 

 peculiar that the supposed upper parts of the specimens should not 

 have been met with ere now, considering that the basal cups are 

 in some beds numerous and fairly well preserved. Similarly the 

 author regards the cup-shaped forms from the Bohemian Silurian, 

 placed b}' Hinde under Acanthochonia as merely incomplete specimens 

 of Ischadites. A significant indication that open cup-shaped speci- 

 mens of Beceptaculites, rather than the assumed conical forms, were 

 present on the sea-bottom is shown by the fact that in an example 

 figured by the author (pi. iii. fig. 8) a Stromatopora has established 

 itself on the inner or upper surface of the wall which must con- 

 sequently have been open and uncovered at the time. 



In well-preserved specimens of Beceptaculites Neptuni, the inner 

 ends or feet of the vertical rays or pillars are inflated, so that they 



