ZOOLOGICAL AND BOTANICAL ASSOCIATION. 203 



rated amounted to seventy. In 1852 I read notes of what had been 

 observed up to that period at the Belfast Meeting of the British Asso- 

 ciation, an abstract of which is published in the Report. 



In 1857 Mr. Hyndman reported to the British Association the pro- 

 ceedings of the Belfast Dredging Committee, and alluded to the occur- 

 rence of a large number of the species of the alluvial beds. The present 

 paper treats the subject in detail, and includes a number of additional 

 species which I have met with this year. 



The greater part of the town of Belfast is built upon alluvial depo- 

 sits of bluish-coloured sand and silt, owing their presence there to the 

 slow but sure instrumentality of that river especially, which is now 

 called the Lagan. It is not many years since a tributary of this stream 

 ran, uncovered, through High-street, which was then, as it still is, the 

 principal thoroughfare of the town. The memory of this is perpetuated 

 by the name Bridge-street being yet given to a locality where no water 

 is to be seen, although the rivulet still wends its way beneath the 

 adjoining pavement. The reclaiming and occupying of much of these 

 beds is within the memory of many besides "the oldest inhabitant;" 

 and one rather extensive area, composed of mud raised in forming a new 

 channel, within the last few years, and designated the Queen's Island, 

 has been converted into a sort of park for public resort, and is fast 

 becoming a favourite promenade. The depositions extend far into the 

 bay, and are extensively exposed, at low water, as far as Holywood, upon 

 the county of Down side, and to "White Abbey, upon that of the county of 

 Antrim. They thus occupy at least a space, the boundaries of which, 

 speaking generally, are not unlike the sides of an isosceles spherical 

 triangle, as it is usually represented upon a plane. The length of each 

 side is four miles, and that of the base about six miles. The localities 

 which were most examined by myself were the embankments raised for 

 the two railways which run along the sides of the bay, and which may 

 be considered as the sides of the triangle, and the cutting made during 

 the progress of the harbour improvements. The latter is in the direc- 

 tion of a straight line from the vertex where we suppose the town to be, 

 bisects the triangle, and is nearly two miles in length. The em- 

 bankments on which the railways lie are formed almost entirely of the 

 sand and mud raised on the spot, and leaving numerous shallow exca- 

 vations. The cuttings, however, made to afford a straight channel, 

 instead of the old tortuous course of the tidal river, presented shells 



