96 FAMILY MILIOLIDA. 



next ; all the " chamberlets" of the same row, however, communicating with each other by 

 a passage that runs continuously through their partitions (see Diagram, p. 52) ; and each 

 " chamherlet " also communicating with the chamberlets of the adjacent rows by perforations 

 in the principal septa. This is, in fact, exactly what we see in the peripheral portion of 

 those thinned-out specimens of discoidal Orbicidince which have but a single row of marginal 

 pores, as will be clearly understood from fig. 1 1 , which represents a part taken from the 

 edge of fig. 6, seen as an opaque object under a much higher magnifying power. At 

 na', ad , ad, ad are seen portions of four of the principal septa which separate from each other 

 the principal chambers or galleries cc', cc', re' ; these galleries are again divided into the 

 " chamberlets " d, d, d by the secondary partitions e, e, e, e, which do not, however, com- 

 pletely separate them from each other ; and the successive galleries communicate with each 

 other by the passages I/, b, that traverse the principal septa, those of the last-formed septum 

 showing themselves as a row of pores upon its external surface. The animal body which 

 occupies the interior of a shell thus divided will obviously consist (as we shall see to be the 

 case in Orlitolites (Plate IV, figs. 14, 23) of a series of principal segments of sarcode, each 

 of which is divided by constrictions into a necklace-like series of sub-segments, strung 

 (as it were) upon a connecting cord ; whilst each principal segment will communicate with 

 the segments anterior and posterior to it, as in Peneroplis, by stolons of sarcode that pass 

 through the septal passages, those of the last segment issuing forth as pseudopodia from the 

 marginal pores. 



140. It is seldom, however, that the arrangement is so simple as in the case just cited; 

 for it much more frequently happens that the space between the two surfaces of the shell 

 exceeds by many times the distance between each septum and that which succeeds it, so that 

 the " chamberlets '' are greatly elongated in the direction perpendicular to the surface. This 

 is shown in fig. 12, which represents the central portion of a section whose plane passes 

 at right angles to that of the spire, and brings into view the successive convolutions 1, 2 2', 

 •3 3' and 4 4', of which each is seen completely to enclose the preceding. Each " chamherlet " 

 is here elongated vertically, and the adjacent " chamberlets " of the same series communicate 

 with one another, not by one passage, but by many (a) ; whilst the successive series also 

 communicate with each other by multiple rows of septal pores {b). In neither set of communica- 

 tions, however, do we observe any great regularity, whether as regards number or arrange- 

 ment. The height of the chambers, with the number of the connecting passages proceeding 

 from them in each direction, is seen to increase progressively from the first-formed convolu- 

 tion (1), whose chambers are disposed upon the simple type previously described, through 

 the second (2 2') and third (3 3') to the fourth (4 4'), in which last it reaches its maximum at 

 no great distance from the centre ; and from this it often diminishes as the chambers 

 extend themselves more and more widely along the margin, which (as already stated) may thin 



out until we find in the peripheral portion a recurrence to the simple type of the central 



The disposition of the sarcode-body that occupies this more complex system of chambers 

 must obviously be modified in correspondence with it, as we shall see in the complex form of 

 OrbitdUfcs (Plate IV, fig. 25). The subdivisions of each principal segment, instead of resembling 

 beads strung upon a single cord, will rather have the form of a row of columns standing side 

 by side, and connected together by numerous bands passing transversely from one to the 



