PLATE XX. 
Figs. 1, 2, 3, and 7.—Naiadites crassa. A series of valves showing the striated 
hinge-plate, and almost obsolete cardinal tooth and pit-like muscle-scars. From 
the Cults Lime Works, Pitlessie, Fife. My Collection. (Page 147.) 
Fig. 4.—Naiadites crassa. A specimen with the valves united, but slightly 
displaced. Same locality. My Collection. (Page 147.) 
Fig. 5.—Naiadites crassa. A dwarf variety. From the Wardie Shales, Wood- 
hall, Water of Leith. My Collection. (Page 147.) 
Fig. 6.—Naiadites crassa. External view of fig. 5. 
Fig. 8.—Naiadites crassa. The worn surface of a left valve. From Cults, 
Pitlessie, Fife. My Collection. (Page 147.) 
Fig. 9.—Naiadites crassa. A specimen exhibiting both valves spread open. 
From the Carboniferous-Limestone Series, Beith, Ayrshire. In the Collection of 
Mr. J. Neilson, of Glasgow. (Page 147.) 
Fig. 10.—Naiadites crassa. A cast showing mantle-lme and muscle-scars. 
From the same locality and Collection. (Page 147.) 
Fig. 11.—Naiadites crassa. A fairly perfect right valve, showing dimensions. 
From Cults Lime Works, Fife. My Collection. (Page 147.) 
Fig. 12.—Carbonicola elegans. A cast showing muscle-scars. From the Calci- 
ferous-Sandstone Series, Hast of Pittenweem. (Page 81.) 
Figs. 13 and 15.—Carbonicola elegans. A right and a left valve. From the 
same locality. (Page 81.) 
Fig. 15 a.—Carbonicola elegans. A line to show the vertical curvature of the 
valve. (Page 81.) 
Fig. 14.—Carbonicola elegans. The hinge enlarged to twice its size. From the 
same locality. (Page 81.) 
