224 Proceedings of the Royal Irish Academy. 



shells appeared to be, in general, coated with a singular growth 

 which I could not account for at the time ; I therefore took some 

 (and, unfortunately, only some) samples of these shells, along with 

 which occurred nodular concretions, seemingly inorganic growths, hut 

 with which I was not familiar. Of these I also took some samples, 

 and, chancing to meet Mr. Doherty, he very kindly gave me some 

 data as to the conditions under which these peculiar shells were 

 found. These data I noted at the time, and herewith reproduce in 

 the accompanying sketch. 



The shells were found at about 2 feet from the bottom of the 

 excavation (caisson), and, consequently, about 22 feet 6 inches below 

 the low-water mark of the river (/in fig.). They rested on a bed 

 of speckled clay, having roots and trunks of trees ; this bed rested on 

 the gravel which formed the lowest stratum of the caisson. Above 

 the shells was a bed of blue clay of 3 feet 10 inches to 4 feet 10 inches 

 thick ; then over that some speckled clay with hazel-nuts, leaves, and 

 vegetable remains imbedded in blue clay, but without shells ; and then 

 above this the washed drift, so characteristic of the bottom of the 

 Lilfey. The specimens taken were put aside for further examination ; 

 but other lines of work caused them to be neglected until the photo- 

 graphic plates accompanying Mr. Foslie's article on Arctic Algse in the 

 Year Book of the Tromso Museum for 1891 called my attention to them 

 anew. I had then no doubt but that they represented some form of 

 coralline alga, but, not being a botanist, I thought it best to send 

 some of my specimens to Mr. Foslie, with the request that he would 

 be good enough to inform me if they were really Lithothamnion, and, 

 if so, to kindly indicate the species. From him I received the following 

 letter : — 



"Trondhjem, Zrd December, 1892. 



" Dear Sir, — The specimens I got from you yesterday belong to Lithothamnioji, 

 but it is probably impossible to determine the species with certainty. The two 

 specimens are very much like Lith. polymorphnm (L.) Aresch (= Melohesia poly- 

 niorpha, Harv. Phyc. Brit.) ; the third one may, perhaps, belong to Lith. fascicu- 

 latimi (= Melobesia fasciculata, Phyc. Brit.) ; but I am not sure, especially of the 

 latter. I return them to-day. 



' ' Believe me, yours truly, 



"M. Foslie." 



The above species are still to be found living in the Bay of 

 Dublin, but apparently not any longer in the mouth of the Biver 

 Liffey. 



