G. W. Tyrrell — Tertiary Dykes of the Clyde Area. 305 



I am fortunately able to identify this form with certainty with 

 the above shell, which Wilckens describes from Cazador, Sierra 

 Contreras, and other places in South Patagonia between Lago 

 Argentino and Last Hope Inlet. He illustrates several examples 

 and says tbat the species is one that does not compare closely with 

 any other Aporrhais known to him. 



Locality. — Selwyn Rapids. I collected two specimens with spire 

 and lip, one of them in fine condition which required to be laboriously 

 chipped out and pieced together again. The spire in the better 

 specimen (Fig. 6) is rather higher and more tapering than in the other. 

 The shell that Hector 1 figures under the name Rostellaria Waiparen&is 

 is probably intended to represent this species. 



EXPLANATION OF PLATES XIX AND XX. 



All figures natural size unless otherwise indicated. All except Pugnellus 



australis are of Upper Senonian age. 



Plate XIX. 



Figs. 



1-4. Pugnellus Marshalli, sp. nov. Selwyn Eapids. 



5. Alaria Suteri, sp. nov. Selwyn Rapids, x 1J nat. size. 



6. Aporrhais gregaria, Wilckens. Selwyn Rapids. 



7. Ditto, another specimen showing upward extension of the lip. Selwyn 



Rapids. 

 8-10. Natica (Euspira) variabilis, C. Moore. Selwyn Rapids. Fig. 10 is 

 x 1J nat. size. 

 11. Turritella sp. Selwyn Rapids, x 2 J nat. size. 

 12-15. Neritopsis (?) Speighti, sp. nov. Selwyn Rapids. Fig. 15 is x 2 nat. size. 



Plate XX. 

 la, b. Pugnellus Waiparensis, sp. nov. Waipara Gorge. 

 2a, b. Pugnellus australis, Marshall, variety. Maestrichtian (?). Wangaloa. 

 3a, b. Pugnellus australis, Marshall, normal form. Wangaloa. 



4. Conchothyra parasitica, McCoy. Waimakariri Gorge. 



5. Ditto, same locality. Another specimen. 



(To be concluded in the August Number.) 



III. — Some Tertiary Dykes of the Clyde Area. 



By G. W. Tyrrell, A.R.C.Sc, F.G.S., Lecturer in Mineralogy and 

 Petrology, Glasgow University. 

 Introduction. 

 rpHE very numerous Tertiary dykes of the Clyde islands (Arran, 

 \_ Bute, and the Cumbraes), and of the adjacent mainland and 

 peninsulas, have been little studied either from the geological or 

 petrographical point of view ; but they are of great interest, not 

 only in themselves, but as providing a link between the dykes of the 

 better known areas of the North of England, and of Skye and Mull. 

 The material is not yet gathered on which could be based a complete 

 account of the series. The present paper is designed to present 

 a full description of a hitherto unrecognized type of Tertiary dyke, 

 typically exposed in the Great Cumbrae, and to indicate its relation- 

 ships to other types already described from Mull and the North of 

 England. Furthermore, a few other dykes from the Clyde area, all of 

 basaltic composition, will be briefly described. 



1 Cat. Ind. and Col. Exhibition, 1886, p. 58, fig. 3. 



DECADE VI. — VOL. IV. — NO. VII. 20 



