120 Mr. Jeffreys on British MuUuaca. 



right as well as the left valve, as shovrn in the plate ; and the de- 

 scription must be amended in this respect. 



Sphserium. I omitted to mention that Mr. Jenyns seems to have 

 been fully aware of the quasi-natatory habits of >S'. calyculatum as 

 well as of his Pisidium obtusale ; and that a satisfactory explanation 

 of this peculiar mode of progression in the former animal would 

 be found at p. 12 of his valuable and interesting Monograph. 



S. calyculatum. In page 35 of the last Number (three lines from 

 the bottom) read "slow" instead of "short." 



Pisidium Recluzianum. For M. Bourguignat's species read P. 

 Reclu*ianum. 



I Montagu Square, Loiidun, Jan. 1859. 



EXPLANATION OF THE PLATES. 

 Plate IL 



Fig. 1. Kellia lactea, hinge of, magnified. 



Fig. 2. Lepton sulcatulum : a, natural size ; b, highly magnified ; c, hinge 

 and teeth of right valve, viewed horizontally ; d, hinge and teeth 

 of left valve, viewed horizontally ; e, hinge and teeth of right 

 valve, showing the ligament; f, hinge and teeth of left valve, 

 showing the ligament ; g, front view, showing the curvature of 

 the margin. 



Fig. 3. Pisidium roseum : a, natural size ; b, front view ; c, side view. 



Fig. 4. Mytilus Galloprovincialis, natural size. 



Fig. 5. M. ungulatus, natural size. 



Fig. 6. Limopsis pellucida : a, natural size ; b, front view, highly magni- 

 fied ; c, side view, highly magnified ; d, hinge, very highly mag- 

 nified ; e, interior margin, very highly magnified. 



Fig. 1 . Terebratula capsula : a, natural size ; b, highly magnified. 



Fig. 8. Argiope cistellula, young : a, natural size ; b, highly magnified. 



Plate IIL 



Fig. U. Chiton gracilis, natural size : a, segment magnified, to show the 

 granulation of the valves and the marginal band; b, a portion of 

 the lingual riband, highly magnified, and showing at A the divi- 

 sion of the falcate teeth . 



Fig. 10. C.Jascicularis, a portion of the lingual riband of, highly magnified. 



Fig. W. C. discrepans, ditto, ditto. 



Fig. 12. Assiminia Gray ana, ditto, ditto. 



Fig. 13. A. littorea, ditto, ditto. 



Fig. 14. Skenea planorbis, ditto, ditto. 



Fig. 15. Euomphalus nitidissimus, ditto, ditto : o, front view ; b, side view. 



Fig. 16. Ditto, animal of : «, natural size; b, highly magnified; c, oper- 

 culum, highlv magnified. 



Fig. 18. Odostomia Eidimoides, var. b. Jefir. : «, natural size ; b, magnified. 



Fig. 19. O. Lukisii: a, natural size; b, magnified. 



Fig. 20. O. alba, var. : a, natural size ; b, magnified. 



Fig. 21. Truncatella Montagui, a portion of the lingual riband of, highly 

 magnified. 



Fig. 22. Recluzia aperta : a, front view, natural size ; b, back view, natural 

 size ; e, magnified to show the sculpture and epidermis. 



Fig. M . Cerithiopsis tiivea : a, natural size; b, magnified. 



