136 ON THE FILLING UP OF RIVER-BEDS AND HARBOURS. 



33. Navicula dilatata. *43. Navicula semen. 



34. gibba. 44. silicnla. 



35. gracilis. 45. viridis. 



36. intequalis. 46. Striatella arcuata. 



*37. - isotauron. 47. Synedra Ulna. 



38. Legumen. 48. Tabellaria trinodis. 



*39. leptogongyla. 49. gastrum. 



40. microstauron. 50. biceps. 



*41. pachyptera. 



*42. scalaris. 51. Lythostylidium rude. 



There are eleven peculiar species in Labrador, but no new genus 

 among them. 



From this list is afforded the very important result, that the northern 

 Eunotia, which are here as elsewhere in northern countries, very nume- 

 rous, occur in this locality with living Closterice, and such Difflugia, 

 which are not preserved in the fossil state. Hitherto they were only 

 known as fossil ; and only one species, near Saltzburgh, has as yet been 

 observed in the living state. They consequently appear to be forms 

 peculiar solely to Northern climes, and will probably be found here and 

 there in the Alps. 



On this account, especially, was a small specimen of marine mud, 

 from the bottom of the sea near Spitzbergen, examined with greater 

 care and precaution. There were found in it nine species of the smallest 

 organisms, among abundant clay ? particles. Three Infusoria with si- 

 licious shields, one Spongia or Spongilla, and four or five species of cal- 

 careous Polythalamia : 



1. Coscinodiscus patina ? 5. Triloculina trigonula. 



2. Navicula aspera. *6. Nonionina arctica. 



3. Synedra Ulna. *7. Rotalia borealis. 



*8. Uvigerina ? borealis. 



4. Spongia acicularis. *9. Serpula ? discus. 



Four of the Polythalamia, are hitherto undescribed. From the in- 

 vestigation of the former twenty-four American localities, which was 

 presented to the Academy in March, there was afforded the sum of two- 

 hundred and fourteen species of the smallest organisms, of which seventy- 

 one were peculiar to America, ninety-four living, and one hundred and 

 twenty fossil. 



The six localities now adduced, which are in great measure new, and em- 

 bracing half the globe, contain one hundred and fifty-four forms, of which 

 one hundred and sixteen are living, thirty-eight fossil, and thirty-one 



