554 DR. CARPENTER'S RESEARCHES ON THE FORAMINIFERA. 



which lie so closely together as to mark-out each band into a series of very elongated 

 cells, which remind us of the oblong superficial cells of the complex type of Orbi- 

 tolites, but are much narrower in proportion to their length. The mouth of the spire 

 is closed by a solid wall, the surface of which is nearly flat, and which is perforated 

 by three, four, or five rows of rounded pores, bearing a very close resemblance to 

 those at the margin of Orbitolites and Orbiculina. 



94. The resemblance suggested by external configuration is fully borne-out by the 

 examination of the internal structure of this genus, as brought into view by longitu- 

 dinal and transverse sections. For it is shown in Plate XXVIII. fig. 24, that the 

 whole organism has originated from a single large nearly-globular cell, around which 

 are successive layers of chambers freely communicating with each other, each layer 

 completely enveloping the preceding, and adding much more to its length than to its 

 diameter. A portion of such a section, more highly magnified, is shown in Plate 

 XXIX. fig. 9. The formation of the successive layers by spiral involution, is well 

 displayed by a series of transverse sections taken at different points, such as are 

 delineated in Plate XXIX. figs. 4 to 7 ; the first (fig. 4) having crossed near the narrow 

 termination of the fusiform shell, and having consequently traversed only the two 

 last-formed turns; the last having crossed near the middle of its length, and having 

 traversed all the six turns by which it was formed. Each whorl seems to be, as to all 

 essential particulars, a repetition of the rest; and hence it will be sufficient to make 

 a detailed examination of only a small part of a section, such as is shown on a larger 

 scale in fig. 8. It is there observed that the spaces occupied by the Barcode-body and 

 bounded by the shell, though far from regular, conform to a certain general plan. 

 Each lamina is made-up (as the surface-furrowing and the marginal pores indicate) 

 of a succession of bands of superimposed cells, of elongated form ; each band answer- 

 ing to one of the annuli of QrbitoUtet. At each point corresponding with the 

 external furrow, the superficial layer of shell sends a prolongation inwards (a, a, a), 

 which thus marks-off the superficial cells more completely from each other than is 

 the case with the subjacent cells; just below this projection is a rounded perforation 

 (b, b, b), which marks the passage of a longitudinal channel ; and at a little distance 

 beneath this is another (c, c, c), which is of very considerable dimensions. Some- 

 times there are more than two such channels; but this is comparatively rare. These 

 channels must have given passage to longitudinal bands of sarcode, running from 

 one end of the lamina to the other, and freely connecting together all the segments 

 occupying the piles of elongated cells of which it is composed. The marginal pores 

 are the orifices of the chambers of the last-formed band ; and it will be observed in 

 Plate XXVIII. fig. 23, that one row of them is contiguous with the preceding whorl 

 of the spire, along which, as is shown in Plate XXIX. fig. 8, there is always a free 

 passage. Thus we may consider the sarcode- body, as in the case of Orbitolite, to be 

 composed of a mass of closely-connected segments, between which a calcareous 

 skeleton grows-up according to a certain tolerably-regular type. It seems to me 



