562 DE. CAEPEXTEE'S EESEAECHES ON THE FOEAMINIFEEA. 



zoophyte, like the Acervulina acinosa of SCHULTZE, but with more of the compactness of 

 Polytrema miniacea. 



219. I now return to the form of Tinoporus on which the genus was originally esta- 

 blished, the T. baculatus of MONTFORT; which agrees closely with T. Iccvis in the 

 fundamental characters of its organization, but differs in being furnished with a variable 

 number of radiating appendages that give it a strong resemblance to Calcarina. Of the 

 specimens in my possession, the greater part present the aspect represented in Plate 

 XVIII. figs. 2, 3, 4, 5, and on a larger scale in fig. 6 ; and these were collected from 

 coral reefs in various parts of the Polynesian Archipelago, my earliest acquisition of 

 them, however, having been from the contents of the stomach of an Echinus taken on 

 the coast of Borneo, which were kindly put into my hands by Dr. J. E. GRAY. I am 

 informed by Mr. DENIS MACDONALD that on certain coral islands which he has par- 

 ticularly examined, these organisms are so extraordinarily abundant, that they accumulate 

 in the lagoons in regular strata, commonly alternating with strata of Orbitolites. The 

 more massive and ruder forms represented in Plate XVIII. figs. 7, 8, 9, 10, occur in 

 Mr. CUMING'S Philippine collection. 



220. External Characters. The typical form of the central portion of T. baculatus 

 (Plate XVIII. figs. 2-6, and in section in Plate XXI. fig. 7) may be considered as an 

 oblate spheroid; sometimes, however, it is nearly spherical, and sometimes it is much 

 flattened out, especially when the body extends itself into the radial prolongations, as 

 in Plate XVIII. fig. 4. Its surface is divided into areolse (fig. 6) very much as in . 

 T. Icems; but the angles of junction of the partitions between the areolse are very 

 commonly occupied by rounded projecting tubercles, strongly resembling those of 

 Calcarina, The number and size of these tubercles vary greatly among different 

 individuals, as will be seen on comparing figs. 2 and 4, Plate XVIII*. From the 

 marginal portion of the central disk there spring a variable number of conical pro- 

 longations having the furrowed surface of those of Calcarina ; and these appear seated 

 (so to speak) upon extensions of the central disk itself, which is sometimes so deeply 

 subdivided at its margin as to resemble the body of a Star-fish (Plate XVIII. figs. 4 

 and 7), the areolar division being continued nearly to the extremity of each ray, and its 

 point only being formed by the furrowed prolongation. These appendages are usually 

 from 4 to 6 in number ; I have occasionally seen only 2, and in no case have I met with 

 more than 8. They usually diverge in or near the equatorial plane ; but they some- 

 times come off in very different directions (Plate XVIII. figs. 8, 10). 



221. Internal Structure. The general organization of T. baculatus, brought into view 

 by sections taken in different directions, does not differ in any essential respect from 

 that of T. Icevis ; the origin of the whole aggregation of chambers in a central cell, their 

 subsequent multiplication both horizontally and vertically, and their methods of com- 

 munication in both directions, being all the same. As already mentioned, I have very 



* They seem to be altogether wanting in the Philippine specimens, being apparently replaced by a 

 multitude of small spines, which give to their surface a hispid aspect. 



