4 SECOND YARKAND MISSION. 



sides and on the edge of the hases of some of the papillae, tubercles and warts of other types. 

 Their resemblance to minute oscula of sponges is superficially evident ; but it is to be shown 

 that one great group of the fossils under consideration does not possess them, that they differ 

 in their number in different parts of the same fossil and in different individuals of the same 

 species. I have called them " pores," and their absence in one of the groups of the fossils 

 has led me to divide these Karakoram Syringosph(erid<je into two genera one with pores on 

 the outer surface is termed Syringosphceria, and that without pores I have dedicated to 

 Stoliczka's memory, terming it Stoliczkaria. 



The method of examination of the fossils is necessarily a simple one. Their surfaces are 

 usually well preserved and not over-weathered, and the insides, in the majority of instances, 

 yield good sections, both radial and tangential. Careful washing adds to the details of the 

 surface, and biting with hydrochloric acid and water is necessary to distinguish tube structure 

 from the intertubular calcite of fossilization which sometimes simulates it. 



The sections, on account of the brilliant opacity and white or white-brown colour of the 

 tubes, can be well studied by reflected light, and indeed it is advisable to do this preparatory 

 to the examination by transmitted rays. The dilute acid is very useful in some confused 

 sections, for it dissolves the infiltrated calcite which exists between the tubes, and leaves their 

 granular wall to a certain extent untouched. The paths of tubes can then be seen by 

 reflected light very well. If the acid is allowed to act too strongly, all structure disappears. 



The tubes, both radial and interradial, are easy to see in the majority of instances, but 

 in one- particular case polarized light and the selenite plate determined the visibility of the 

 structures, which were hidden amongst a confused mass of calcite. The calcite which was 

 introduced during fossilization fills the tubes as well as their interspaces, and it has taken on 

 definite or indefinite cleavage planes. These must be studied under polarized light, for the dark 

 lines they produce to ordinary transmitted light, and which simulate coenenchymal structure 

 can then be decided to be only divisions between crystals or parts of different polarizing 

 influence on the ray. 



Low powers of the microscope suffice for most of the examination, but a good ^-inch 

 object glass is required to distinguish the granules and granule-spiculate elements of the 

 tubes. 



No other form of fossilization but that by calcite has been noticed, and silica does not 

 enter into the composition of the bodies. 



On examining the surface of a rugged or tuberculate specimen of either of these genera 

 with a hand lens, a reticulate appearance is seen between the projections. In very good speci- 

 mens, on the ordinary level of the surface, after biting with dilute acid, or sometimes without 

 this proceeding, this reticulation resolves itself into a gyrose tubulation ; the tubes coming to 

 the surface, running along it in close proximity, dipping down again suddenly and re-appear- 

 ing, and sometimes bifurcating. Between the tubes is a more or less linear interspace filled 

 with dark calcite. Weathering sometimes has destroyed the tubulation and left the thin 

 interspace to look like a mesh, or the interspace has been left void, the tubules remaining. 



Besides this reticulation, there are in some types numerous, and in others but a few 

 minute openings from y^- 1 ^ to ^^ mcn i n diameter, and they have a margin or tube layer. 

 They are sometimes separate, and at others they are clearly the outside opening of one of the 

 superficial tubes just mentioned. Usually the caliber of the tubes is filled with brownish 

 coloured calcite, or with granular carbonate of lime, but in some instances the presence of a 

 very delicate tube wall, unattached by its outside to any structure, is evident. 



