484 JDr. H. Woodimrd — Synopsis of the Sj^ecies of 



back cliffs, and that the present rainfall, small though it is, is yet 

 delivered in such heavy showers as to produce violent and destructive 

 floods. It is probable also that there may have been a period of 

 greater rainfall at the close of the Pleistocene, of which there seems 

 to be evidence in the deposits surrounding the Dead Sea and in the 

 older alluvia of the Nile itself. The cutting back of the Cataracts of 

 the Nile has been already referred to. A curious memorial of this 

 exists in the diverted channel of the river at Assouan, along which 

 the railway at that place runs. According to the measurements of 

 Mr. Hawkshaw, it is seven miles and a half in length ; and 100 

 feet above the present level of the Lower Nile above the cataract. 

 Thus it belongs to a time when a large amount of cutting remained to 

 be done, before the river attained to its present state. In this channel 

 are old banks of Nile mud, which may be seen behind Assouan and 

 also near Philee, and have been described by Dr. Leith Adams. 



It thus appears that the Nile, like most other great rivers, has 

 been only in part the excavator of its own bed, and that it has been 

 indebted to preparations made for it in very ancient times, though 

 mainly to the changes connected with and consequent on the great 

 elevations at the close of the Eocene Tertiary, and the marine 

 erosions taking place in still later submergence and re-elevation. 

 In connection with this, it is interesting to note the recency of 

 the present alluvial plain, and the probability that in the first or 

 second continental period, or in both, the Nile discharged itself to 

 the eastward into the Arabian desert at the head of the Ked Sea. 



Ekrata. 



No. VII. Page 291, line 12 from bottom, /or " Alsilis" read Silsilis. 



,, ,, 292, „ 16 from top. /or " horizontal" >Y«(^ slightly inclined. 



,, „ 292, ,, 20 from bottom, /or "Ahmeen" re«t? Ahmar. 



,, ,, 292, last line, /or " leeward " rea^? seaward. 



No. IX. „ 387, first line, for " SenefEeh " read Geneffeh. 



,, ,, 387, description of plate, for "here row " read horizon. 



,, ,, 388, line 9 from bottom, for "there " read those. 



,, ,, 391, footnote, /or " Zib " read Tib. 



,, ,, 392, line 17 from bottom, /or "about" rmt? almost. 



,, ,, 392, ,, 3 from bottom, for " Ostrea succinea'^ read Ostrea succini. 



11. — Synopsis of the Genera and Species of Cakboniferous 



Limestone Trilobites. 



By Henry ■Woodward, LL.D., F.E.S., F.G.S. 



(PLATE XVI.) 



SINCE the appearance of my paper in the Geological Magazine, 

 1883, Decade II. Vol. X. pp. 534-542, the following species 

 have been added to the list of British Carboniferous Limestone 

 Trilobites, and will form a part of the forthcoming volume of the 

 Palffiontographical Society for the present year. 



Geiffithides brevispinus, H. Woodw., 1884. Plate XVI. Fig. 4. 



Griffithides brevispinus, H. Woodw., Pal. Soc. Mon. Carb. Trilob. part ii. 1884, p. 

 39, plate vii. figs. 7, 8. 



Among the various specimens received from Mr. Eobert Craig, of 



