REPORT ON THE RADIOLARIA. 1745 



plane, at right and left; their maximum number is three pairs, viz.: — (F) the paired 

 pectoral tubes (as the foremost), directed forwards ; (G) the paired frontal or lateral 

 tubes, placed either in the frontal axis of the valve, or in a neighbouring axis, directed 

 towards the right and left pole (PI. 127, figs. 4-8, g 4 and g 5); (H) the paired tergal 

 tubes, directed backwards (constant in all Cceloplegmida). The origin of these tubes is 

 rather variable, since they arise in nearly allied species, sometimes independently of one 

 another, at other times united at the base. But a closer comparison of them in the 

 different species ^^dll demonstrate their homology, caused by constant heredity. 



The terminal ramules of the brushes, which form the subspherical " fork-thicket " in 

 the Ccelothohda, the outer " lattice-mantle " in the CcBloplegmida, are constantly armed 

 at the distal ends either with spathiUse or with anchor-pencils, bunches of those most 

 elegant spinulate threads, which l)ear at the free end an anchor, or a whorl of two, three, 

 or four recurved teeth (PL 122, fig. 8 ; PL 127, fig. 10; PL 128, figs. 1, 6). The 

 pencils are usuaUy dichotomously branched, their threads zig-zag or delicately serrate, 

 often armed with very small recurved denticles, and the anchor teeth (commonly three 

 or four) are usually smooth on the convex outer, serrate on the concave inner edge. The 

 entire surface of the subspherical thicket in the Coelotholida, and of the polyhedral lattice- 

 mantle in the Cceloplegmida, is armed with thousands of those most elegant spathUlse, or 

 anchor-pencils. 



The " fork-thicket " of the Coelotholida is identical with that of the Coelodendrida, and 

 is composed only of the innumerable dichotomous branches of the hollow tubes. It envelops 

 the two central valves and the enclosed central capsule in the same way as in the Coelo- 

 dendrida. But the Coelotholida differ from these latter in constantly possessing a 

 rhinocanna and two frenulse. The entire form of this thicket, which in the few sjaecies 

 observed was never complete, but always more or less destroj^ed, is usually prol:)ably 

 subspherical or polyhedral, sometimes cordate or kidney-shaped. Its surface is densely 

 studded with thousands of spathiUse. Its diameter is about four to eight times as great 

 as that of the enclosed bivalve shell. 



The " lattice-mantle " of the Cceloplegmida, which replaces in this subfamily the fork- 

 thicket of the Coelotholida, is always produced by the anastomoses of the distal ramules 

 of the brushes, and of those branches of the styles which do not proceed over the surface 

 of the mantle. Its network is always very irregular, and composed of polygonal meshes of 

 very different sizes. Usually it is quite simple, and may be compared with the cortical 

 sheU of the Disphserida. More rarely it is more or less spongy. Its surfiice is densely 

 studded with thousands of spathillse or anchor-pencils. The entire form of the lattice- 

 mantle is always symmetrically polyhedral, since its dorsal and ventral halves are 

 S5'mmetrically developed on both sides of the equatorial plane, and therefore correspond 

 perfectly to the enclosed smaller halves of the central bivalve shell. The two valves of 

 the lattice-mantle (dorsal and ventral valves) are never really united and grown together, 



(ZOOL. CHALL. EXP. — PART XL. 1886.) Ef 219 



