16 SECOND YARKAND MISSION. 



very diffused, the tubes being very irregular in size, shape, and position in the section. In 

 some places the tubes are very close, bifurcate, as in the other instances, and are more or less 

 around the circular groups. There is not much difference in the size of the tubes, which 

 vary from -3^ to j^o inch. There are spots without any tube structure, and these are 

 circumscribed and are the relics of old pores, passed by during the radial growth of the 

 body. 



In radial sections there is in many places such an exact relation in shape between the 

 tube-structure, whether reticulate or radial, and the interspaces, that it is very difficult to 

 distinguish interspaces filled with clear calcite from very transparent tubes. So many 

 circular spaces exist, 3^0 inch in diameter, in these parts of the section, that they may be 

 taken for tube sections, surrounded by a whitish and rather opaque calcite. But they are 

 really interspaces, the true tubes having the translucent walls. The radial series is not, on 

 the whole, very distinguishable from the interradial, but the pores exist as vacant elongate 

 spaces bounded by tubes all around, and bridged over tangentially by tube reticulation. 

 They are not lined by any special structure. 



The minute structure of the tubes is a finely granular substance (carbonate of lime), 

 lightish red to transmitted light, and there are dark granules like minute dendrites. There 

 is no trace of a coenenchyma, and the fossilization simulates many structures, which are, 

 however, readily resolved by even low powers of the microscope. 



The height of the body is IYS inch, and the breadth 2 inches. 



V. THE SPECIES OF STOLICZKARIA. 



One species of this genus is amongst the collection, and its forms are readily known by 

 their great size, minutely, but not sharply, granular appearance, and the absence of pores. 



STOLICZKARIA GRANTJLATA, Duncan. Plate II, Eig. 5 ; Plate III, Figs. 5, 6, 7. 



The body is large, spheroidal, and symmetrical ; it is covered with a vast number of 

 minute eminences and interspaces. The eminences are separated by about their own breadth, 

 or they may be closer, touching at their bases ; they are usually circular in outline, low, 

 flat or rounded at the free extremity, and are about as tall as their base is broad. There are 

 usually five, and the corresponding interspaces, in y^ inch. In some places the bases are con- 

 tinuous so as to form long narrow gyrose ridges, and in others they are absent, the circular 

 base existing only. Here and there are some larger ones, and minute granules are inter- 

 spersed. 



Rather large tubes are on the outside and flanks of the eminences, and they open around 

 and close within the circular top edge. They pass on to the spaces between the eminences, 

 and are closely crowded, very bent, and form a dense reticulation, some opening there 

 outwards. 



The inner or central part of the upper surface of the eminences has a few, rather wide- 

 apart tubes opening there ; they are radial and small, and are readily distinguished from the 

 interradial series around. Where an eminence is rudimentary, the central radial tubes 

 may be seen separated by a little interspace from the dense reticulation of larger and closer 

 interradial tubes. 



