EXPLANATION OF PLATE XXXIV. 



Fig. 13. Yontio-, T. rrnren, Lamarrk, 35 Tinn. long-, ponimenciiig' tn bniTow 

 ill (lead coral. 



,, 14. T. croccii, 18 mill. long'. 



,, IT). T. i-riicfd, 81 null, long, to show disproportionate increase of 

 pedal nppi'tnie. 



16. Riglit valve of Tri'ilirmi. 2 1 mm. liigli. 



„ 17. Hinge of ditto. 



,, IS. Left valve of Triihtcnn, 20 mm. high. 



„ 19. Hinge of ditto. 



