G. S. Kinahan — Re-arranged Glacial Drift. Ill 



EXPLANATION OF PLATE V. 



Fig. 1, — Bithyrocaris ovalis, W. and E., specimen having both valves preserved united 

 along the mesial line. 



Fig. 2. — Bithyrocaris granulata, "W. and E., the left half of the carapace only pre- 

 served. 



Fig. 3. ditto. 



Fig. 4. glabra, "W, and E., the left half of the carapace only preserved. 



Fig. 5. "W. and E., the right half of the carapace only pre- 

 served. 



Figs. 1-5 were all obtained from the Black Carboniferous shales overlying 

 the Galderwood cement-stone, E. Kilbride, Lanarkshire. 



Fig. 6. — Bithyrocaris ? striata, W. and E., part of the left valve only preserved. 

 Lower Old Eed Sandstone, Carmichael Burn, S.E. of Lanark. 



Fig. 7. — The small specimen of Bithyrocaris tricornis, Scouler, referred to in the 

 former part of this paper, see Geol. Mag. 1873, Vol. X. p. 485, as 

 showing "the same infolding of the lateral margins as the larger ex- 

 ample displays." (See Vol. X. PI. XVI. Figs. 2 and 3.) 



I 



III. — GrLAOIAIiOID OR Re-ARRANGED GlACIAL DrIFT. 



By G. H. Kinahan, M.R.I.A. 



N many places in Ireland, but conspicuous in the S.E. portion, 

 there is a Glacialoid drift (that is, a drift very similar in aspect 

 to some of the typical Glacial drift). This drift will be found in 

 places above the shelly drifts of Wicklow and Wexford, and 

 has led Prof. Harkness, F.R.S., to believe that in those counties 

 there is evidence for two distinct periods of glacial drifts, one below 

 and the other above the shelly drift. His classification has been 

 adopted by Mr. A. BelP and others; still there does not appear 

 to be evidence in Ireland for two distinct ages of glacial drift, 

 separated by an interval, represented by sub-aqueous accumulations 

 (sand, gravel, marl-clay, &c.), and the reasons for this conclusion 

 will be given in this paper. 



There is reason for supposing that in Ireland since the great 

 Glacial period there have been four marked changes in the level of 

 the country : — 



I. — During the first, the land sank from 250 to 350 feet lower 

 than at present. This we will call the Period of the 300 feet sea 

 heacJi or the Esker sea period. 



II. — At the second the land was stationary for some time, while 

 between 70 and 120 feet lower than it now is. This may be called 

 the Time of the 100 feet sea beach. 



III. — At the third there was a rest when the land was from 20 to 

 30 feet lower than now. This I propose to call the Time of the 25 feei 

 sea beach. 



TV. — At the fourth the land was at least 30 feet higher than it is 

 now. The subsequent depression by which it was brought to its 

 present level appears to be still in progress in certain places. 



These changes seem to have been more or less prevalent over the 

 whole country, but not always uniform, as since the Glacial period 

 the drifts have been afi"ected by faults, some of very recent date, and 



^ Palaeontology of the Post-Glacial Drift of Ireland, by Alfred Bell, Geol. Mag. 

 1873, Yol. X. p. 447. 



