PLATE III. 



Fig. 1. — Myalina Redesdalensis. Portion of a right valve. My Collection. 

 (Page 109.) 



Fig. 1 a. — The same specimen showing shelf for anterior adductor muscle, 

 striated hinge-plate, terminal umbo, and deep umbonal cavity. (Page 109.) 



Fig. 1 b. — The same specimen, showing the extent and size of the hinge-plate, 

 and its relation to the shelf ( X ) for the anterior and adductor muscle. (Page 109.) 



Fig. 2. — Myalina Redesdalensis. Viewed from above and behind. The only 

 specimen which has been obtained from Redesdale in a fairly perfect condition. 

 Found by Mr. John Dunn, and now in the possession of Mr. R. Howse, of 

 Newcastle-on-Tyne. (Page 109.) 



Fig. 3. — Myalina Redesdalensis. Portion of a left valve, showing the extensive 

 flat anterior surface. My Collection. (Page 109.) 



Fig. 4. — Myalina Redesdalensis. Profile view, with anterior side much fore- 

 shortened to show the angular ridge. (Page 109.) 



Fig. 5. — Myalina Redesdalensis. The anterior portion of a left valve. 

 (Page 109.) 



Fig. 6. — Myalina Vemeuilii. A cast of the interior, showing pallia! line, 

 posterior adductor scar, and the non-terminal umbo seen in all casts. Collection 

 of Mr. J. Neilson. (Page 115.) 



Fig. 7. — Myalina Redesdalensis. A fragment, to show the thickness and 

 contour of the valve. My Collection. (Page 109.) 



Fig. 8. — Myalina Redesdalensis. Fragment of a valve, showing at X the 

 byssal aperture. My Collection. (Page 109.) 



Fig. 9. — Myalina Redesdalensis. A fragment, showing the distance of the 

 pallial line from the edge of the valve. My Collection. (Page 109.) 



Fig. 10. — Myalina Redesdalensis. A fragment, showing the imbrication of the 

 lines of growth as they pass over the lower portion of the ridge. My Collection, 

 (Page 109.) 



Fig. 11. — Myalina Redesdalensis. Portion of a right valve, showing the details 

 of the anterior part of the shell ; X marking the anterior adductor scar. My 

 Collection. (Page 109.) 



Fig. 12. — Myalina Redesdalensis. A fragment about the centre of the hinge- 

 line, showing (x) the pit-like scars for the pedal muscles. My Collection. 

 (Page 109.) 



Figs. 13 and 13 a. — Myalina Redesdalensis. Two views of the central portion 

 of the hinge-plate, with the pedal muscle scars at X- My Collection. (Page 109.) 



Fig. 13 b. — The same specimen shown in contour, to show the angle at which 

 the hinge-plate joins the rest of the shell, and its relative thickness. (Page 109.) 



With the exception of Fig. 6, all the specimens are from the Redesdale Shales 

 in connection with the Redesdale Ironstone, and probably the upper portion. 

 The specimens were all obtained by Mr. John Dunn, who kindly presented them 

 to me. 



