POST-TERTIARY FOSSILIFEROUS DEPOSITS. 



39 



imagine that the term " recent/' which had been usually appHed to such deposits, was 

 not rigidly correct ; and he made another excavation and published a list of shells which 

 established the glacial character of the beds.^ 



No further examination of the Dalmuir beds was carried on until we made an 

 ■excavation in the east side of the stream to the north of the bridge on the Dumbarton 

 Road, in the immediately adjacent field, about half way down. At this point the shells 

 are discovered in great abundance, in the position described by Dr. Thompson, beneath 

 an overlying bed of sand and gravel. Of eleven pounds of the dry clay from this bed 

 three pounds two ounces were lost in washing through a sieve of ninety-six cross threads 

 to the inch, leaving seven pounds fourteen ounces of a residue. Three and a half pounds 

 of this residue were retained in a sieve of ^-inch mesh, and consisted chiefly of small 

 stones of trap, quartz, and sandstone ; a few were quite smooth and only rounded at the 

 corners, others less or more irregular. Many of the polished stones were fractured, and 

 some few finely striated. The bulk of the shelly debris in this portion was made up of 

 Mytilm edidis and M. modiolus. The other portion of the residue (four pounds six 

 ounces) consisted chiefly of sand, mixed with the plates and spines of EcJiini and many 

 species of small Mollusca. 



Besides this north patch of shell-bearing clay, there is another bed a few hundred 

 yards to the south which was laid open by a cutting for the water-course of the Dalmuir 

 paper-mill, and extends along the north side of the bank, about forty yards east of the 

 burn. The shell-bearing clay rises about four feet above the water-course, when it is 

 overlain by two feet of waterworn gravel. The upper portion of the shell-bearing clay 

 is more sandy than the lower, which contains more stones, most of them water-worn, 

 some rounded off at the corners, a few angular, and a few vfith well-marked striations. 

 Beneath the upper clay, however, is a bed of sand about six inches in thickness, in 

 which many of the peculiarly Arctic Mollusca are especially large and strong. Troplion 

 clathratmn, e. g., is very abundant, while it is scarce in the upper part of the clay. The 

 sand is followed by a stiff blue Boulder Clay (common through the district) in which no 

 shells occur. 



The complete section is, therefore, as follows : 



1. Sand and gravel . . . . 2| ft. to 6 ft. 



2. Shell-bearing clay . . . .2ft. 



a. Upper part mixed with sand. 

 h. Lower part not sandy. 



3. Shell-bearing sand . . . .6 inches. 



4. Boulder Clay, not pierced through. 



1 ' Memoirs of Wernerian Soc.,' vol. viii, p. 50. 



