222 LOWER PALEOZOIC HYOLITHIDJE FROM GIRVAN. 



Figs. 6-8. Hyolithes subcrispatus. Dorsal faces ( x 2). 

 ,, 9-9a. Hyolithes sylvestris. 9, dorsal face ( x 2|) ; 9a, portion of surface ( x 5). 

 ,, 10-12. Hyolithes (Orthotheca) subexcavatus. 10, dorsal face; 10a, cross-section; 11, side view of 



ventral face (all x 2|) ; 12, portion of surface of ventral face ( x 5). 

 ,, 13-15. Hyolithes (Orthotheca) subornatus. 13, ventral face ( x 2£) ; 13a, portion of surface of ditto 



( x 5) ; 14, interior from dorsal side ( x 2£) ; 15, ditto ( x 2). 

 ,, 16-23a. Hyolithes (Orthotheca) thraivensis. 16, side view; 17, dorsal face; 18, ditto; 19, ventral 



face; 20, side view of ventral face; 21, cross-section; 22, ventral face; 23, ditto; 



23a, cross-section. (All x 2.) 

 ,, 24, 25. Hyolithes (Orthotheca) thraivensis, var. granuliferus. 24, impression of ventral face ( x 2£) ; 



24a, portion of surface of ditto ( x 5) ; 25, cast of same specimen ( x 2|). 

 ,, 26-28. Ceratotheca 1 snbuncata. Side views ( x 2). 



Plate III. 



Figs. 1-3. Ceratotheca 1 balclatchiensis. 1, side view ; 2, ventral view ; 3, ditto, showing apex. 



(Allx 2.) 

 ,, 4-5. Pterotheca drummuckensis. 4, cast ; 5, impression showing internal plate. (Both x 2.) 

 ,, 6-13. Pterotheca girvanensis. 6, showing internal plate ; 10, showing marginal projection of carina ; 



11, internal cast; 12, impression of part of exterior; 13, showing internal plate (all x 2). 



6-10 from Balclatchie ; 11-13 from Ardmillan. 

 ,, 14-16. Pterotheca multidecorata. 14, 15, 16 (all x 2); 15a, portion of surface ( x 5). 

 ,, 17,17a. Pterotheca simplex. 17a, cross-section ; 17, 17a (all x 2|). 

 ,, 18-20. Pterotheca muttochensis. (All x 2.) 



