H. W.. Pearson—Changes in the Sea-Level. 115. 
isolated imperfect plate of a Chiton, in which the sides are bent down 
rather more acutely and suddenly leaving a narrower dorsum, but the 
ornamentation and general shape appear to be indistinguishable from 
the Llandovery form above described. 
EXPLANATION OF PLATE IY. 
Fie. 1.— Anatifopsis balelatchiensis, sp.nov. Left valve. x 3. Balclatchie Beds: 
Balclatchie. 
»,  2.—Ditto. Ditto. _x 3. Same horizon and locality. 
», 3.—Ditto. Ditto. x 3. Same horizon and locality. 
», 4.—Ditto. Ornamentation of surface. x 26. 
5, 5.—Pinnocaris curvata, sp.nov. Left valve. x 2. Starfish Bed: Drummuck 
Group, Thraive Glen. 
», 6.—Ditto. Ditto. x 2. Same horizon and locality. 
>,  %.—Ditto. Anterior portion of right valve, showing ornamentation. x 2. 
Same horizon and locality. 
>,  8.—Solenocaris solenoides, Young. Posterior four segments with caudal spine 
attached. x 3. Balclatchie Beds: Balclatchie. ; 
‘,, 9.--Ditto. Ornamentation of surface of spine of same specimen. x 25. 
5, 10.—Ceratiocaris (Solenocaris?) sp. Caudal spine. x 3. Balclatchie Beds: 
Dow Hill. 
»» ll.—Ditto. Ditto. x 8. Same horizon and locality. 
>, 12.—Helminthochiton Grayie, H. Woodward. Internal cast of portion of 
body, showing the seven posterior segments. x 2. Starfish Bed: Drummuck 
Group, Thraive Glen. 
», 13.—Chiton sp. Side view. x 2. Saugh Hill Group, Woodland Point. 
», 14.—Ditto. Same specimen, top view. x 2. 
V.—DEFoRMATIOX AND VARIATION IN THE SEA-LEVEL.? 
By H. W. Pearson. 
HANGES in the relative level of sea and land along the oceanic 
borders of the globe seem to have been in continual progress 
during the entire historic period. Too slow and gradual for direct 
observation, they can only be detected through comparison of ancient 
with modern maps, records, or statements. This comparison has now, in 
hundreds of cases, been made, and it is well established that stability of 
coastline is the exception, movement of elevation or depression the rule. 
In one region, it has been observed, the sea for long periods of time 
has been in continual retreat; at another location it has been long 
advancing over the land, while at some third point it seems to have 
remained fixed in position. 
In the days of Linnzus and Celsius, when the uplift of the Baltic 
shores was first recognized, it was believed that this motion could be 
best explained by assuming an actual depression, or falling, in the 
surface of the sea, but since the time of Playfair this idea has been 
entirely abandoned, and all authorities now hold that these motions 
must be due to movement in the crust of the earth. 
Playfair’s law, which has thus remained in possession of the field, 
has recently been restated by Professor Fairchild in the 5th edition 
of Leconte’s ‘‘ Elements of Geology” (p. 145), as follows :— 
‘¢ But by the principle of hydrostatic level, it is clearly impossible 
that the ocean should rise or fall permanently at one place without 
1 For former paper, see Grou. Mac., 1901, pp. 167, 223, and 253. 
