Vol. 59.] 



BOULDER-CLAY IN ICELAND. 



359 



being very rare. The malacologist of the Zoological Museum of 

 Copenhagen, Hr. Ad. S. Jensen, who has been good enough to 

 undertake the determination of the fossils in question, has sent me 

 the following list of species : — 



Astarte borealis, Chemn. 



Portlandia lenticula, Moll. (?), nucleus. 



Leda pernula, Muell., nucleus. 



Mya, truncata, L. 

 Saxicava arctica, L. 

 Trophon clathratus, L. 



Of the foregoing species, Astarte borealis is the shell most com- 

 monly met with in our Boulder-Clay, and next to it in abundance 



Fig. 2. — Section near Bidandsliofdi. 



erratic 



Concealed 



Thin basalt-dyke. 



/= Volcanic tuffs and breccias, 

 reaching a thickness of 300 to 

 400 feet. 



e = Glaciated dolerite. 



d— Conglomerate, about 'JO feet. 



c = Conglomerate, about 30 feet. 



b - Shelly Boulder-Clay, 70 to 80 feet, 

 including 10 feet or so of lami- 

 nated sandy clay (/3). 



a=' Fundamental basalt.' 



are Saxicava arctica and Mya truncata. Hr. Jensen calls attention 

 to the great thickuess of the valves of the two last-named species, 



1 [Hr. Jensen is now of opinion that this is a nucleus of Portlandia (Yoldia) 

 arctica, Gray. A shepherd- boy from Mavahlid, Helgi Salomonsson, whom I 

 took to the locality and requested especially to look out for such things as this 

 nucleus, later collected, besides other shells, three specimens of Portlandia arctica, 

 Gray, which have been kindly determined by Hr. Jensen. These are : — 



(1) A specimen with both valves, partly crushed, but certainly recognizable 

 by its sculpture. 



(2) A nucleus with some remains of the valves ; the foremost end is broken 

 off, but the specimen has probably been at least 22 millimetres long. 



(3) A nucleus (the valves still partly preserved) about 16 mm. in length. — 

 June 25th, 1903.'] 



