18 PB0CEEDINQ8 OF THE NATIONAL MUSEUM. vol.54. 



Plate 10. 



Fig. 1. Placiphorella borealis Pilsbry [94], exterior view of first, third, and last 

 valves; camera drawing; X 2 J. 



2. Interior view of same; same scale. 



3. Posterior view of fifth valve; same scale. 



4. Basal portion of large spinose bristle from anterior lobe of girdle of same 



specimen; camera outline from a mount in balsam; X 60. On most 

 bristles the spines appear to be more closely placed than is indicated in 

 the drawing. 



5. Portion of ventral surface of anterior lobe of same specimen, showing patches 



of spinelets; camera drawing from a mount in balsam; X 60. 



6. Basal portion of marginal spinose bristle from anterior lobe of girdle of same 



specimen; camera drawing from a mount in balsam; X 60. 



7. Isolated spines from ventral surface of anterior lobe of same specimen; 



camera drawing from a mount in balsam; X 150. 



8. Isolated girdle and bristle spines from same specimen ; camera drawing from 



a mount in balsam; X 150. 



9. Isolated teeth from radula of same specimen; camera drawing from a mount 



in balsam; X 60. 



Note. — The drawings on Plates 1, 4, 6, and 8 are from the brush of Mr. E. Russel 

 Lord-Wood. 



The majority of the figures as originally prepared were intended for plates of a 

 larger size than those used in these Proceedings. Then again the plates first made 

 were destroyed by fire and the make-up of several of them subsequently rearranged. 

 This resulted in changes in the degree of magnification of the figures at a time when 

 most of the specimens were no longer available for checking. There is therefore an 

 unavoidable source of possible error in the magnifications as given. 



