DONKINj ON DIATOMACEiE. 11 



below tlie liigh-water level. In sucli situation it is therefore 

 covered with fresh water for a short period during ebb tide, 

 and with salt water for several hours during the flow. It is 

 not, however, confined to the beach, but forms an olive stratum 

 on the surface of the piers, stones, and piles of our harbours, 

 between the high and low water level, and may be looked 

 upon as the species which occurs in most abundance on our 

 coasts. 



In the gatherings I have made of this species I have 

 observed that all the specimens, in a very short space of time, 

 congregated and adhered around any extraneous matter present 

 in the gathering, and that the groups thus formed adhered 

 with wonderful tenacity. This phenomenon I have frequently 

 observed under the microscope, and have been astonished to 

 observe numberless individuals simultaneously directing their 

 course towards the same object, as if controlled by an in- 

 fluence higher than physical force, to which alone the move- 

 ments of the DiatomacccB have been referred by many ob- 

 servers. 



Hab. Chibburn mouth, Druridge Bay, Lyne Mouth, Blyth 

 Harbour, Tynemouth. /'f'l-^ [i) 



10. Amjjhora ocellata, n. sp. — j^orm on F. V. broad, 

 rectangular, extremities very slightly rounded, colourless; 

 hoop on dorsal surface transversely and very delicately 

 striated ; valve inflated, finely striated, with a broad, hyaline 

 band extending across it from posterior margin to central 

 nodule; central nodule indefinite, marginal. Length, about 

 •0028" ; breadth, about -0014/'. 



The hyaline, transverse band gives rise to an opaque, eye- 

 shaped spot on each margin of the frustule, when seen on the 

 F. V. From a comparison of specimens of botii forms, I feel 

 satisfied that this species is distinct from A. Icevis, Greg. >. 

 ('Trans. R. Soc. Edin.,^ vol. xxi, part iv, pi. iv, fig. 74). ; £ K.i^ ) 



11. Amphora naviculacea, n. sp. — Form on F.V. rectangular,' 

 angles slightly rounded, valve highly convex, median line 

 gently curved; striae on dorsal or outer half of valve continuous, 

 and nearly parallel ; an inner or ventral half coarser, inter- 

 rupted, and absent opposite central nodule, strongly divergent 

 on either side of it, and strongly convergent near terminal 

 nodules. Length, fi'om 0030" to -0035" ; breadth of F. V. 

 about -0011". 



This species strongly resembles a Navicula in its F. V., 

 though the want of symmetry of the valve on either side of 

 the median line, even observable in this view of the frustule, 

 easily determines its generic position. 



Hab, Cresswell, common, May, 1858. 



