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period of retrogradation. Thus the present terraced trenches of the fan- 

 building rivers cannot be relics of the retrogradational phase, and must 

 therefore be due to some other cause and of a later date. (2.) The profile of the 

 existing terraces is not such as would have resulted from shore-recession. 



Fig. 4. — Diagrammatic section of a river-fan, showing form of 

 terraces developed during a period of retrogradation 

 following the normal progradation of the shore-line 

 by a copious supply of waste. 



This is clearly shown by a comparison of fig. 3 and fig. 4 ; the former shows 

 the form and arrangement of the terraces of the Ohau Valley, and the latter, 

 terraces developed in a fan truncated and trenched as a result of retro- 

 gradation of the shore-line by sea erosion. 



Aet. XVI.- 



-Ceina, an Aberrant Genus of the Amphvpodan Family 

 Talitridae. 



By Charles Chilton, M.A., D.Sc, LL.D., F.L.S., Hector Memorial Medal- 

 list, Hon. Member Roy. Soc. N.S.W., Professor of Biologv, Canterbury 

 College, N.Z. 



[Bead before the Philosopfiical Institute of Canterbury, 18th December, 1918 ; received by 

 Editor, 30th December, 1918 ; issued separately, 26th May, 1919.] 



The genus Ceina was established in 1893 by Delia Valle for the single 

 species C. egregia (Chilton), which had been described in 1883 under the 

 genus Nicea Nicolet, a genus now considered to be identical with Hijale 

 H. Rathke. The species was placed under Nicea because it appeared in 

 many respects to come near to Nicea rubra G. M. Thomson, N. fimbriata 

 G. M. Thomson, and other species then referred to Nicea ; but it was 

 pointed out at the time that it differed in several important characters, 

 and some points in the original description were left more or less 

 doubtful. Stebbing in 1888 (p. 1712) mentioned the species, stating that 

 its generic position was not quite free from doubt. In establishing the new 



