114 FAMILY MILIOLIDA. 



even in different zones of the same disk (^t 173, 178). The pores /,/ at the margin of the 

 disk are disposed, as in the simpler type, between the projections formed by the convexities of 

 the chamberlets ; but they are less regularly circular than in the simple type, and the sur- 

 rounding annuli of shell is less distinct. The number of pores in each vertical row 

 is by no means constant, even in different parts of the margin of the same annulus; and their 

 disposition is far from regular (fig. 10), as they seldom form rows that seem exactly con- 

 tinuous with each other horizontally, while the vertical rows are often interrupted, the two 

 adjacent rows then usually inclining towards each other. 



166. Internal Structure. — The disks of this complex type are not distinguished from 

 those of the simple type already described, by any difference in the structure of the 

 " primitive disk ; " and there is frequently nothing specially characteristic in the structure of 

 the zones that immediately surround it. Each of the peripheral zones, however, consists of 

 two superficial layers, and of an intermediate stratum (Plate IX, figs. 7, 8, 9) ; these will now 

 be described seriatim. The superficial layers are formed of the (usually) oblong chamberlets, 

 whose contour is indicated by the surface-markings ; when they are laid open horizontally, 

 by rubbing away the thin shell which covers them in (fig. 7, i, i, i), it is seen that the 

 floor of each chamberlet has an aperture at either end ; but no communication can be 

 traced, either through the side-walls between the contiguous chamberlets of the same zone, 

 or through the end-walls, between the chamberlets of successive zones. Moreover, there is 

 no such alternating arrangement of the chamberlets of successive zones, as we have seen to 

 prevail in the simpler type (^ 157) ; and they altogether seem to be quite independent one 

 of another. When this superficial layer is examined in a vertical section having a radial 

 direction (Plate IX, fig. 8), it is seen that the floors of its chamberlets are formed by the 

 expanded summits (/, /,) of the irregular septa which separate from each other the successive 

 zones of columnar chamberlets of the intermediate stratum {r, c, c', c,) ; and that the 

 apertures at the two ends of the floor are the entrances to passages (w, ;«'), which lead 

 obliquely downwards (the passages on either side of the partition between two successive 

 chamberlets of the superficial layer always inclining towards each other) towards these 

 cavities. It is observable, moreover, that just at the point at which the contiguous passages 

 meet each other, there is always a round aperture (//, //) in the partition which divides the 

 contiguous chamberlets of each zone; and when, in a horizontal section, the superficial 

 chamberlets have been entirely ground away, so as to lay open the most superficial part of 

 the intermediate stratum, this part is found to be traversed in each zone by a continuous 

 circular gallery (Plate IX, figs. 7, 9, /i, //,//.,) with large rounded openings that lead into the 

 columnar chamberlets beneath. The meaning of this arrangement becomes obvious, when 

 We examine the disposition of the animal substance which occupies these cavities ; for we 

 find, as might have been anticipated, tliat the superficial cells are filled with segments of 

 sarcode of corresponding shape (Plate IV, figs. 24, 25, a, a'); and that whilst these have 

 no direct connexion with one another, each of them is connected by means of fleshy 

 peduncles with the annular stolons d, b' that run along its extremities ; whilst from the under 

 side of these annular stolons (fig. 25) descend the thick columns of sarcode {ce, c'c), which 

 occupy the columnar cells of the intermediate stratimi. The absence of any essential 

 dependence of the segments of the superficial and of those of the intermediate strata upon 



