514 A. G. MacGregov and F. R. Ennos — 



oval foramina corresponding to the first and second pillars of the living 

 chamber. Near the right-hand top corner part of the lid is broken away, 

 showing the pits produced by the monoliform rays and the concentric 

 shelly walls. Rather under one-half natural size. Author's collection. 

 EiG. 2. — Barrettia of. monilifera ; Woodward. Same locality. A young 

 specimen with the upper valve in place, partly crushed into the visceral 

 cavity. Rather over one-third natural size. 2a. Top view ; at the bottom 

 of the figure is seen the embayment of the margin of the shell. 26. Side 

 view of both valves conjoined. The decoration of lid and sides is well 

 seen on young examples such as this one. Same collection. 



Plate XX, 



Fig. 1. — Barrettia cf. monilifera ; Woodward. Upper Cretaceous. Haughton 

 Hall, near Green Island, Western Jamaica. Specimen of the lower or 

 conical attached valve viewed from above. The lid is missing and the 

 living chamber has been cleaned out. Around the living chamber are 

 . seen the pits of varying. size and depth into which shelly processes from 

 the under side of the top valve fitted. Near the left-hand side a portion 

 of the top valve remains. Slightly over one-third natural size. Author's 

 collection. 



Fig. 2. — Same species. Same locality. Specimen with both valves conjoined, 

 the central part of the lid almost completely crushed into the living 

 chamber, viewed partly from above and partly from the side. The top 

 lid is very thin and is weathered away in places, especialljr near the right- 

 hand top edge of the figure, where the monilif orm rays like strings of beads 

 can be seen. In other parts the saucer-like depressions on the surface of 

 the top valve are visible. Towards the lower part of the figure the top 

 lid is partly grown over by oysters. Slightly under one-third natural 

 size. Same collection. 



Fig. 3. — Barrettia cf. multilirata ; Whitfield ; var. cylinclrica nov. Same 

 locality. Specimen with both valves conjoined, part of the lid broken 

 away at the top right-hand edge. Rather over one-third natural size. 

 Same collection. 



Fig. 4. — Gardita ( Verier icardia) cf. <<iibcomplanafa ; d'Archiac. Same locality. 

 Right valve. Natural size. Same collection. 



Fig. 5. — Avellana {Eriptyclia ?) cf. decurtata ; Zekeli. Same locality. Natural 

 size. Same collection. 



The Traprain haw Phonolite. 



Part I : Nepheline, Analcite, Sodalite, and Olivine in 

 the Traprain Law^ Phonolite. 



By A. G. MacGregor, M.C, B.Sc. 



Part II : Analysis of the Traprain Law Phonolite. 



By F. E. Ennos, B.A., B.Sc, A.I.C. 



Part I. 

 A RE-EXAMINATION of tJie trachytoid phonolite of Traprain 

 -^ Law was undertaken on the suggestion of Mr. E. B. Bailey, 

 in order to determine the characteristics and mode of occurrence of 

 the nepheline contained in it. The slides examined were those of 

 the Geological Survey collection and nine new ones specially cut 

 from material recently obtained. During the course of the 

 examination sodalite and olivine were detected in the rock. 

 These minerals have not been mentioned in previous accounts of 



