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mistaken for it, and yet essentially differing from it in its plan of 

 structure. This is the case with a type of which some remarkable 

 specimens occur in Mr. Cuming's collection, and of which some 

 smaller examples have been kindly put into the author's hands by 

 Dr. J. E. Gray. As it seems to be identical with the body described 

 by Montfort under the designation Tinoporus baculatus, it may be 

 right to retain that name, although it had been abandoned under 

 the impression that it was a mere synonym of Calcarina. The 

 structure of this body will be better understood after the description 

 of a simpler form, which seems to be generally diffused through the 

 seas of warmer latitudes, but of which the most remarkable examples 

 present themselves in Mr. Jukes's Australian dredgings. Its shape 

 is extremely variable, being sometimes an almost perfect sphere, in 

 other cases resembling the lower half of a sugar-loaf, whilst in other 

 cases again it is a very irregular depressed cone. It seems originally 

 to have grown attached to zoophytes, corals, &c., since it frequently 

 presents indications of such former attachment, though it is rarely 

 to be met with otherwise than free. It is, moreover, very closely 

 allied in structure to the body which has been termed Polytrema 

 miniaceum, under the belief that it was a Polyzoan Coral, but whose 

 Foraminiferous affinities have been already perceived by Dr. Gray, 

 who has proposed for it the generic name of Pustulipora. 



In the commencement of its growth, this organism seems closely 

 to resemble Planorbulina, being formed of an assemblage of cham- 

 bers arranged on one plane, spirally towards the centre, but irregularly 

 clustered towards the circumference ; each chamber communicating 

 by single large septal orifices with the two contiguous chambers of 

 the same row, whilst its walls are perforated with numerous large 

 pseudopodian foramina. This first-formed plane, however, is after- 

 wards covered-in above and below by numerous successive layers of 

 similar cells, which are piled one upon another in very regular rows ; 

 the original spiral type of growth being altogether lost in these super- 

 posed layers. In this mode the organism comes to present a near 

 relationship to the fossil genus Orbitoides* ; the principal difference 

 being that the superposed layers are not so completely differentiated 

 from the original median layer in Tinoporus as they are in Orbitoides. 



* See the author's account of the structure of that genus in the Quarterly 

 Journal of the Geological Society, vol. vi. 1850, p. 32. 



