ZOOLOGICAL AND BOTANICAL ASSOCIATION. 209 



more numerous and much finer, the nearer to the course of the river 

 they were found. The size attained was sometimes remarkable, the 

 length of one being 2 J inches, and its breadth lg. Mr. Hyndman re- 

 cords it in his report: — "At a depth of 30 feet in sinking a well at 

 Durham-street mill; at 18 feet at Linfield mill; on the muddy banks 

 of the River Lagan, nearly as far up as the tide now flows. It has not 

 been found living." I have also remarked it in abundance in the post 

 Pleistocene beds of Clontarf, near Dublin. 



Donax anatinm (Lamarck). 

 This species has been met with by Mr. Millen in the light-house de- 

 posits, and is at present an inhabitant of the bay. 



Mactra elliptica (Brown). 



Occurred pretty often in the sandy deposits, and preserved its glossy 

 epidermis in a striking degree. No examples of more than average size 

 were found. It is still enumerated amongst the inhabitants of the 

 harbour. 



Mactra subtruncata (Da Costa). 



A large number of fine examples of this species was found in the 

 sandy mud of the beds, with their regular concentric grooves and yel- 

 lowish tinged cinereous epidermis in good preparation. One example, 

 selected rather for its fine appearance than for its size, measured more 

 than one inch an^ a quarter in length, and in breadth exactly one inch. 

 Shells of this species were brought up in the mud raised by the steam- 

 dredges in clearing the bed of the river opposite the site of the former 

 Harbour Office between the foot of High-street and Waring-street. It 

 was here that a sandy ford across the Lagan existed for many centuries, 

 and gave name to the town, Belfeirste, "town of the ford." There is a 

 continuous chain of notices of this ford in the records of the neighbour- 

 hood, extending from the year 667, in which a battle was fought be- 

 tween the Ulidian8 and Picts upon the Ford. As it became an impedi- 

 ment to the navigation of the modern sea-port in 1786, it was mostly 

 removed, and was found to consist of a finished work of stones and wood, 

 upon the substratum of a sandy bar formed by the confluence of the 

 Lagan and High-street river with the tidal sea- water. It was lately 

 completely obliterated by the Harbour Commissioners ; and it was after 

 clearing away the sand that they came upon the mud, which must, 



