I9I3- HlNCH. — Shelly Dtift of Co. Mayo. 5 
4. The Tellina Boulder-clay of the Belderrig district 
occurs at the mouth of the Belderrig river, about 50 feet 
above sea-level, and at Fiddawntawnanauneen at an 
elevation of about 120 feet. The clay, which is highly 
calcareous, contains many erratics, striated pebbles of 
limestone, granite, mica-schists, sandstones, and quartz 
rock. Numerous shell-fragments also occur at Belderrig. 
The really striking feature of this clay is the presence 
of large numbers of complete valves of Tellina calcarea. 
This bivalve, which is synonymous with T. proxima and T. 
lata, and is restricted at the present day to the colder 
regions of the Northern Hemisphere, has an average length 
and height of if and i.^ inches, and like all the Telhnas 
has no special strength of shell, yet after heavy rain a dozen 
unbroken valves may be easily collected. Many of the 
valves have such sharp outline, and retain their epidermis, 
colour, and glaze to such an extent as to be indistinguishable 
from modern specimens. The extraordinarily perfect state 
of preservation of these Belderrig Tellinas when compared 
with the fragmentary condition of the shells obtained from 
the till of Glenulra and the Owenbehy raised the question 
as to a possible later origin of the Belderrig Boulder-clay ; 
and the occurrence in the Clyde valley of Tellina proxima 
(^calcarea) as the chief shell in clays usually classed as 
late Glacial supported this view. The latter date 
of the Belderrig Boulder-clay was practically settled by 
finding in one of the streams near Fiddawntawnanauneen, 
that the Tellina clay rested on a clay which differed in no 
respect from the brownish Boulder-clay of the district. 
The following shells were foimd at Belderrig, usualty in a 
fragmentary condition. 
Ostrea edulis Cyprina islandica. 
Mytilus, sp. TelUna balthica 
Nuculana (Leda) pernula Glycimeris (Panopea) norvegica 
Cardium edule Turritella communis. 
5. The vSands and Gravels of the district do not present 
any special points of interest, as they are the usual extremely 
variable fluvio-glacial deposits, so characteristic of the 
closing stages of the Ice Age. In Glenulra shell -fragments 
are very abundant, but did not add any new species to the 
list obtained from the Till. 
