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FIRST REPORT on the MARINE FAUNA in the 



Neighbourhood of PENMAENMAWR. 



By Isaac C. Thompson, F.R.M.S. 



During the month of July, 1885, I spent a few weeks in the 

 neighbourhood of Penmaenmawr examining the Marine 

 Fauna of the district, by dredging and tow-netting from a 

 boat, and also by collecting on the rocks at low water. 



The district explored included the Mouth of the Menai 

 Straits, the sea between the Welsh Coast and Puffin Island 

 (seven miles across), and, in the other direction, towards the 

 Great Ormes Head, as well as the region about Colwyn Bay. 



The depth in this locality rarely exceeds four fathoms, 

 and the sea bottom is generally clayey and sandy ; patches of 

 round stony masses were occasionally met with. 



Near to Puffin Island I dredged over a large mussel bed, 

 a very prolific region, yielding quantities of Zoophytes, the 

 abode of innumerable Amphipoda. A similar mussel bed 

 was passed over at the East side of the Little Ormes Head, 

 near Colwyn Bay. 



On one rather stormy day early in July the tow-net 

 yielded a large number of specimens of the Megalopa stage 

 of crabs ; although they were conspicuously absent from all 

 subsequent tow-net gatherings. 



During the whole period tow-net work was much impeded 

 by the abundance of some peculiar gelatinous bodies which 

 were distributed throughout the sea. These little bodies 

 were always distinctly visible on holding a bottle of sea water 

 up to the light. They varied in size from yV to t,, of an 

 inch in diameter, and were spherical or oblong in form, 



