PLATE I {continued). 



Fig. 



50. Athyris pectinifera, J. de C. Sowerby. Slightly enlarged. Humbleton hill. A portion of the 



spinose expansions have been removed on one side. Collection of Mr. 

 Kirkby. 



51. — — A specimen, showing the spirals. 



52. — — (Enlarged.) Humbleton hill. Collection of Mr. Kirkby. 



53. — — Interior, showing the larger portion of the spirals, but better explained 



in Plate II, fig. 2. Humbleton. Collection of Mr. Howse. 



54. — — From Sowerby's 'Min. Con.,' tab. 616. 



55. — — A few of the spinose expansions, enlarged to show how they sometimes 



expand at their extremities. Humbleton hill. Collection of Mr. 

 Kirkby. 



56. — — Internal cast of the ventral valve. The letter N denotes the space left by 



the dental or rostral plates. 



