210 Royal Society. 



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. Tn 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. 

 Now in Tinoporus baculatus we often find columns of solid shell- 

 substance interposed between the angular partitions of the piles of 

 superposed cells, just as they are in Orbitoides, their summits being 

 visible on the surface as projecting tubercles ; these columns are 

 perforated with pseudopodian canals, which are extensions of the pores 

 in the walls of the chambers over which they lie. And the peculiar 

 stellate projections which give to this species so much the aspect of 

 a Calcarina are for the most part formed of a similar growth ; for 

 though the chambered structure is continued for a short distance as a 

 conical protuberance into the base of each, yet this cone is invested 

 and extended by a sheath of solid shell-substanpe, which is perforated 

 by pseudopodian tubes extending through it from the chambers. 



The last type of Foraminiferous structure described in this com- 

 munication is one which appears to furnish a highly interesting link 

 of connexion between Foraminifera and Sponges. Its nature was at 

 first entirely misunderstood, the specimens in Mr. Cuming's collec- 

 tion having been supposed, not only by Mr. Cuming, but by other con- 

 chologists, to be shells of a sessile Cirripede. Their external resem- 

 blance might readily justify such an inference, since they are irre- 

 gular cones, apparently composed of distinct valves, attached by a 

 spreading base to the surface of shells or corals, and having a single 



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

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



