LOWER PALAEOZOIC HYOLITHLD./E FROM GIRVAN. 221 



Relations of the Girvan Hyolithid^e to those of other Areas. 

 It is a remarkable fact that all the Girvan species, except one or possibly two which 

 occur in Co. Tyrone, appear to be peculiar and new. Afber a careful comparison 

 with all the well-known English and Welsh species, it does not seem possible to regard 

 any as identical, and the relationship of any of them is not very close. Many, however, 

 of the Girvan forms are allied to Scandinavian ones, of which we have such a full and 

 detailed knowledge owing to Holm's memoir. A few show affinities with Bohemian 

 species. It may be noticed that amongst the Girvan Conularice, Miss Slater * 

 recognised one species identical with a Scandinavian form, and more than one possessing 

 considerable affinities with those from that region. 



Conclusion. 



By the foregoing study of the Hyolithidce the Girvan area is seen to contain an 

 unusually rich and varied assemblage of members of the group. The interest of 

 them is heightened by the local restriction and peculiarity of the species, and by the 

 frequently good state of preservation of the material, which renders it possible to define 

 their characters with greater precision than is usual in dealing with members of the 

 same group from other British localities. 



EXPLANATION OF PLATES. 

 Plate I. 



Figs. 1-6. Hyolithes ardmillanensis. 1, ventral face ; 2, dorsal face ; 2a, cross-section ; 3, dorsal face ; 



4, ventral face; 5, dorsal face; 6, operculum. (All x 2.) 

 7-9a. Hyolithes asteroideus. 7, ventral face; 7a, cross-section; 8, dorsal face; 9, ventral face; 



9a, cross-section. (All x 2.) 

 10-13. Hyolithes candidus. 10, dorsal face; 11, 12, ventral face (all x 2h) ; 13, ornamentation of 



ventral face ( x 5). 

 14-14'i. Hyolithes columbanus. 14, dorsal face; 14a, side view ; 146, ventral face; 14c, cross-section 



(all x 2) ; 14a", portion of dorsal face near lip ( x 3). 

 15-17«. Hyolithes girvanensis. 15, ventral face; 16, dorsal face; 17, 17a, dorsal and ventral faces of 



same shell. (All x 2£.) 

 18-21. Hyolithes immemor. 18, 18a, dorsal face, impression and cast; 19, dorsal face; 20, ventral 



face (three-quarter view, right side); 21, dorsal face. (All x 2|.) 



Plate II. 



Fig. 1 . Hyolithes immemor. Operculum ( x 2^). 



Figs. 2-26. Hyolithes multipunctatus. 2, ventral face ; 2a, cross-section (both x 2) ; 2b, ornamentation 

 ( x 3). a 



„ 3-5. Hyolithes penkillensis. Dorsal faces ( x 2|). 



* Slater, Mon. Brit. Conularice (Palseont. Soc), 1907, pp. 16, 21, 31. 



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