PLATE III (continued). 



Fig. 



34. Strophalosia lamellosa, var. Humbletonensis, King. Natural size, from specimens in the 



collection of Mr. Kirkby. Humbleton hill. 



3o. — — var. Humbletonensis, King. Is an enlarged representation of the 



dorsal valve and beak of the ventral one, from specimens in the 

 collections of Messrs. Howse and Kirkby. In this specimen the 

 area is visible, but it is sometimes concealed from the incurvation 

 of the beak. 



.'36\ — Ventral valve, to show the great length of the adpressed spines. 



Humbleton. Collection of Mr. Kirkby. 



37. — — ■ Internal cast of the interior of the dorsal valve. Humbleton. Collec- 



tion of Mr, Kirkby. 



> s - — Impression of the dorsal valve (enlarged), from Ryhope-field House, 



proving that, although the valve in question is not spiniferous in 

 the great majority of individuals, they did exist in some few 

 examples. Collection of Mr. Kirkby. 



39. — — A gutta-percha impression of the interior of the dorsal valve, to show 



the articulation of the valves, muscular and reaiform impressions, 

 from a specimen iu Queen's College, Galway. Humbleton. The 

 internal cast from which the impression here represented was 

 taken is the same figured by Professor King in pi. xii, fig. 30, of 

 his Monograph ; but the Professor's illustration was not quite 

 correctly drawn. 



40. — A fragment of the dorsal valve, greatly magnified, to show how the 



striae, which cover the surface, augment by intercalation and 

 bifurcation the distance between m and n, representing 2 lines. 



41. — Enlarged portion of the ventral valve, to show how the long adpressed 



spines sometimes originated from two or three striae, forming the 

 base of a single spine. 



