552 DE. CAEPENTEE'S EESEAECHES ON THE FOBAMINIFEEA. 



myself, however, by the comparison of a large number of specimens, that so continuous 

 a gradation presents itself between the smoothest and the most hispid specimens, as 

 to render the attempt to separate them specifically altogether futile ; and Mr. W. K. 

 PAKKEB, who has examined a yet larger number of specimens, fully confirms this 

 conclusion. Moreover the internal structure of these hispid specimens, as shown in 

 horizontal section (Plate XX. fig. 8), shows no departure whatever from the ordinary 

 type. 



199. Returning, now, to the external aspect of the fully-developed Calcarina, we have 

 to notice that each surface of the disk is very commonly elevated, especially in its central 

 portion, into rounded tubercles, more or less closely set together (Plate XIX. figs. 3, 4). 

 These are sometimes large and prominent, and present the semitransparent appearance 

 which is common among the like tubercles of Ojoerculina (^[ 146); more commonly, 

 however, they are less conspicuous either as to size, prominence, or distinctive aspect ; 

 and sometimes they are almost or altogether wanting (figs. 1, 2). Yet it is seldom, if 

 ever, that they are absent from both surfaces of the disk ; and it is more common to find 

 them deficient on the surface nearest to the apex of the spire, than on that on which its 

 last-formed chambers are visible. And even when no prominent tubercles are present, a 

 distinction may be generally made out by careful examination in the parts of the surface 

 corresponding to their usual situation. For whilst the exterior of the disk is marked, 

 more or less conspicuously, with minute punctations (figs. 1, 3, 4), these are not to be 

 seen on its tuberculated prominences ; and the like deficiency is generally to be noted 

 in circular spots of the surface, even when it is not raised into tubercles. Occasionally, 

 though rarely, not even this mark of differentiation is seen, the punctations being 

 uniformly distributed over the surface, which is in that case always the one nearest the 

 apex of the spire. 



200. The surface of the spines is marked, more or less conspicuously, by a longitu- 

 dinal furrowing (figs. 1, 3, 4), not unlike that of the " marginal cord " of Operculina 

 (^[156). The furrows maintain a general parallelism, but there are frequent inoscu- 

 lations between them ; and punctations marking the orifices of deeper canals are often 

 to be noticed at the bottom of the furrows. 



201. One important feature of the external aspect of the disk has yet to be mentioned ; 

 namely, the indication of a spire, which more or less distinctly presents itself on one of 

 its surfaces (Fig. II. u, Fig. III. D, G, H). This indication is sometimes limited to two or 

 three chambers ; but more commonly about half a turn may be distinguished, the spire 

 becoming absorbed (as it were) into the solid mass of the disk, as we trace it backwards. 

 The walls of the last-formed chambers, where entirely disengaged from the disk, are 

 extremely thin (Plate XIX. fig. 4), so that it is rare to find them perfect ; and an opening 

 formed by the fracture of the wall of the newest chamber has been mistaken by MM. 

 FICHTEL and MOLL, and apparently by M. D'OEBIGNY also, for the true aperture of the 

 shell, which, as will presently appear, is of an entirely different character, and not easily 

 to be distinguished. The prominent surface of the walls of the conspicuous chambers 



