228 PROF. H. A. NICHOLSON AND DK. J. MURIE ON THE 



under the name o£ ParTceria, in au exhaustive and fully illustrated 

 monograph (Phil. Trans, vol. clix. p. 721). Dr. Carpenter sug- 

 gested to us in our present inquiry that we should find Parheria 

 to be related to the Stromatoporoids ; and he kindly placed at our 

 disposal a number of his microscopic preparations of the former. 

 We have also carefully examined specimens of Parheria by means 

 of sections prepared by ourselves, Parkeria, as is well known, 

 occurs in the form of globular bodies from about half an inch up 

 to two inches or more in diameter. When these spheres are laid 

 open, they are seen to be " formed of a series of concentric la- 

 mellce of ' labyrinthic structure,' partially separated by concen- 

 trically disposed interspaces, but connected at intervals by ' radial 

 processes,' which consist of large tubes that are surrounded (in 

 all except the five or six innermost layers) by labyrinthic struc- 

 ture resembling that of the concentric lamellss." The entire 

 skeleton is made up of minute sand-grains and granules of phos- 

 phate of lime cemented together by a cement of carbonate of 

 lime. In the fact that both Parkeria and the typical Stromato- 

 poroids are composed of concentric laminae, with interlaminar 

 spaces and radial pillars, there is a striking resemblance estab- 

 lished, enough to warrant the supposition that both might belong 

 to the same systematic grouj). The general resemblance of struc- 

 ture thus indicated is even further increased when we compare 

 with non-infiltrated specimens of Parkeria the decalcified casts in 

 silica of the sarcode-chambers of a typical Stromatoporoid. We 

 have, however, satisfied ourselves that no real relationship of 

 afilnity exists between Parkeria and Stromatopora ; and the prin- 

 cipal grounds upon which this conclusion is based are the follow- 

 ing:— 



(a) Parkeria possesses a skeleton essentially identical with 

 that of the "arenaceous" Eoraminifera generally, consisting, 

 namely, of distinct grains of sand and phosphate of lime cemented 

 together, Stromatopora and its allies, on the other hand, possess 

 a calcareous skeleton, as we have formerly shown ; and in no case 

 can it be shown to be composed of definite and distinct grains 

 of any mineral substance. 



(V) All the parts of the skeleton of Parkeria have that com- 

 plex construction out of minute irregular chambers, to which 

 Dr, Carpenter applied the epithet "labyrinthic." On the other 

 hand, the concentric laminae and radial pillars of the Stromato- 

 poroids do not exhibit any labyrinthic structui'e, though occasion- 



