Lower Palaeozoic Pocks of the South of Scotland . 59 
the secondary rays tapering to an acute point. The entire 
length of one of the rays is *37 millim. I have only seen a 
single imperfect specimen of this form in the chert from 
Hartree Hill. 
EXPLANATION OF THE PLATES. 
Plate III. 
Fig. 1. S typtosphcera anti qua , sp. n. 
Fig. 2. Spongoplegma priscum, sp. n. The inner medullary sphere is 
shown by the dark central portion. 
Fig. 3. Dorysphcera reticulata , sp. n. The radial spine in this specimen 
has been partially dislocated, and some of the mesh-apertures 
are infilled with the dark staining material. 
Fig. 4. Dorysphcera laxa , sp. n. In this specimen the radial spine is 
viewed obliquely. 
Fig . 5. Dorysphcera nucula , sp. n. 
Fig. 6. Stauroplegma barbatum, sp. n. The medullary sphere in this 
specimen is indicated by the partially clear central space. 
Fig. 7. Dorydictyum simplex , sp. n. 
Fig. 8. Doryplegma gracile , sp. n. 
Fig. 9. Doryplegma nasutum , sp. n. The lower portion of this specimen 
has been displaced by a quartz-vein. The inner or medullary 
sphere is indicated by the darker central area. 
Fig. 10. Diploplegma cinctum , sp. n. 
Fig. 11. Haliomma vetustum f sp. n. The mesh-apertures in the specimen 
are indistinct, owing to the dark infilling. 
Plate IV. 
Fig. 1. Acanthosphcera antiqua } sp. n. The specimen is imperfect, a por- 
tion to the right having been cut off by a quartz-vein. 
Fig. 2. Triposphcera hastata , sp. n. In this specimen only one of the three 
radial spines is preserved entire, the bases only of the other two 
remain. The inner sphere is partially clear and has not been 
infilled with the opaque material like the outer sphere. 
Fig. 3. Dorysphcera reticulata , sp. n. 
Fig. 4. Stauroplegma diffusum, sp. n. A quartz-vein traverses the right- 
hand portion of the specimen. 
Fig. 5. Stauroplegma brevispina, sp. n. The upper portion has been dis- 
placed by a quartz- vein. 
Fig. 6. Stauroplegma compressum y sp. n. 
Fig. 7. Staurodoras gracilis , sp. n. Only the base of the lower spine 
remains. A quartz-vein traverses the specimen. 
Fig. 8. Haliomma cornutum ) sp. n. 
Fig. 9. Triposphcera Feachii ) sp. n. 
Fig. 10. Triposphcera densa f sp. n. 
Fig. 11. Triposphcera armata , sp. n. 
Fig. 12. Sphcerozoum patulum, sp. n. A geminate spicule, the rays im- 
perfect, referred to this species. 
The figures have been drawn by transmitted light from microscopic 
sections of the chert-rock in which the Radiolaria are imbedded ; they 
are all enlarged to the same scale of 200 diameters. The specimens are 
all from the same zone in the Ordovician or Lower Silurian strata of the 
Southern Uplands of Scotland ; the particular localities are given in the 
text. 
