6 SECOND YARKAND MISSION. 



In other types the limitation and surrounding of the radial series of tubes by the larger 

 and more extensive series of reticulating ones is readily seen in tangential sections close to 

 the surface, but it becomes rather confused at some distance within, on account of the obli- 

 quity of the radial series in relation to the surface. For they start as it were from a central 

 point in the fossil, and radiate in all directions, increasing in width and in their number of tubes. 

 The distinction between the two series is readily made, however, for the interradial is usually 

 the largest in extent and its tubes are eminently bifurcate and form close reticulations, bend- 

 ing often suddenly and showing geniculate outlines. Tangential sections further in, even 

 although they are less distinct, show that the breadth of the radial and interradial series 

 diminishes centrally. 



In one group of the fossils, forming the genus Stoliczkaria, no trace of the surface- 

 pores exists and no vestige of any of them can be distinguished in sections. But in the 

 other group forming the genus Syringosphceria, the pores can usually be distinguished in 

 some parts of the fossil, besides the surface, especially in tangential sections, as circum- 

 scribed structureless spaces filled with clear or opaque calcite. It does not appear that the 

 tubes which pass out of the pores, at the surface, are restricted to one particular series, and 

 they may belong to the radial group, or more frequently to the reticulate or interradial set. 



Radial sections of the fossils show structures which correspond to those seen in tangential 

 sections, and the morphology of the forms is divisible into two categories. In one, the 

 structures consist of numerous conical congeries of bifurcating radial tubes, the apex being 

 central and the base at the surface of the body ; and of a reticulate tubulation separating 

 the cones, joining their external tubes and arising from them. The cones and the inter- 

 medial reticulation increase in size towards and at the surface of the body, on which are 

 widely or closely-placed tubes passing radially, tangentially, and obliquely. Hence the 

 surface of the body presents the ends of the radial tubes and those of the reticulation, and it 

 is mainly composed of the tubes which are placed tangentially over the circumference. 



In those types of the Syringosphceridce, where there are eminences with radial tubes 

 surrounded by much space occupied with tube-reticulation, the radial sections illustrate the 

 structure of the whole admirably. One of these sections may be considered in three parts 

 in order to explain the morphology. Near the centre fossilization confuses the structure, 

 but it appears that a simple tubular structure arises from around a foreign body, such as a 

 many-chambered Foraminifer, or that one tube branches suddenly in every direction. The 

 tubes radiate in separate groups, each tube bifurcating frequently as it recedes outwards, 

 and there are frequent lateral tubes connecting them together. Hence the mass of tubes 

 increases in the number of its tubes, and forms in section a more or less triangular outline, 

 the apex being towards the centre of the body. At the same time the tubes of the outside 

 of the triangle or longitudinal section of the cone give off others which form in part the 

 reticulation of the interradial part. This is small at first, but increases in section in the 

 middle of the body. 



In the middle of the body, in sections, the radial series is seen to be broader and the 

 interradial to form large meshes. Close to the surface of the body, in sections, the radial 

 series of tubes is seen to bifurcate to the last, and to open directly on an eminence so far 

 as its central tubes are concerned, and many of the outer tubes pass obliquely on the flanks 

 and open at the top. The interradial series also opens by its radial tubes at the surface and 

 by its oblique tubes, but those parallel with the circumference pass over it. (Plate III, Figs. 

 1, 4, 6). 



