360 



Nos. 11, 12, 13, and 14, form a very remarkable panduriform 

 group, the first two having entire costse, like Pinnularia alpina, 

 the last two moniliform strise. The author, on this account, names 

 the first, No. 11, Navicula, after De Briberson, and the second 

 doubtfully, as no description of N. nitida, Sm., has yet appeared. 

 The two others are quite new. The author here stated that he had 

 found in this deposit N. didyma with costse, so that he considers it 

 possible that all these forms may belong to only one species ; but the 

 point requires investigation. 



24. Cocconeif? radiata, n. sp. 



25. „ lamprosticta, n. sp. 



26. Amphora elegans, n. sp. 



15. Navicula clavata, n. sp. 



16. Pinnularia longa, n. sp. 



17. „ fortis, n. sp. 



18. „ Ergadensis, n. sp. 



19. „ inflexa, n. sp. 



20. „ acutiuscula, n. sp. 



21. Stauroneis amphioxys, n. sp. 



22. Cocconeis distans, n. sp., inaccu- 



rately figured in Part I. 



23. Cocconeis costata, n. sp., a more 

 characteristic specimen than that 

 figured in Part I. 



The three last form a very remarkable group, either a subgenus 

 or. a new genus. To this group belongs also Amphora Arcus, of 

 which a part is figured in Part I. 



34. Campylodiscus simulans, n. sp. 



The author showed that this form so much resembles, in its mark- 

 ings, Surirellafastuosay as figured in Part I., that these two genera 

 probably form but one. 



35. Campylodiscus bicruciatus, n. sp. ( 38. Nitzschia socialis, n. sp. 



36. Nitzschia distans, n. sp. 39. Amphiprora minor, n. sp. 



37. „ insignis, n. sp. | 40. „ recta, n. sp. 



The remaining forms will be described on a future occasion. 



2. Theory of the Free Vibration of a Linear Series of Elastic 

 Bodies. Part II. By Edward Sang, Esq. 



I. The first part of this paper was occupied with the discussion 

 of the validity of Newton's Theory of the Propagation of Sound. 

 In order to discover the velocity of sound, Newton supposes a series 

 of particles ranged in a straight line to be set to vibrate all equally 

 and isochronously, but the epoch of vibration to vary gradually along 

 the line ; and he then investigates the circumstances under which 

 such a vibration is possible. The true result of the investigation is 

 this, — that if the two extreme particles bo kept vibrating by some 



