10 DICKIE, ON DIATOMACEH AND MOLLUSCA. 
Lpithemia turgida, Sm. Pinnularia viridis, Sm. 
45 gibba, Wirtz. 5s divergens, Sm. 
= zebra, Kitz. I radiosa, Sm. 
»  Hyndmanni, Sm. (very  Synedra delicatissima, Sm. 
rare). Cocconema cymbiforme, Khr. 
Amphora ovalis, Kitz. = cistula, Eby. 
Cocconeis placentula, Khy. Gomphonema vibrio, Khr. 
Campylodiscus costatus, Sm. (very es olivaceum, Ehr. 
rare). if capitatum, Khr. 
Surirella ovata, Sm. (very rare). a tenellum, Sm. 
Navicula ovalis, Sm. Odontidium mutabile, Sm. 
Bs Jirma, Witz. Denticula sinuata, Sm. 
es liber, Kitz. Orthosira orichalcea, Sm. 
. patula, Sm. Mastogloia Grevillii, Sm. 
$3 rhomboides, Khr. 
Three or four of these were not at first observed by me, 
but recognised by Professor G. Walker-Arnott, of Glasgow, 
to whom specimens were sent. 
Mr, Lee, in his notice of the tumulus,* states that its shape 
was somewhat different from that of others in Ireland, “being 
more flattened and less elevated ;” and further adds—“ This 
may be accounted for by the continued action of the waters 
of the lake, which probably surrounded it for centuries ; the 
former existence of which is proved, not only by the geological 
formation of the locality, but by the remains of fresh-water 
shells, and lake Infusoria found in the substratum on which 
the tumulus stands.” Respecting this inference, I would 
remark that it is totally at variance with the facts observed. 
It is obvious that a tumulus, consisting of comparatively 
loose material, could not have existed for any length of time 
exposed to the action of water, often more or less liable to 
agitation by winds and floods. But supposing the mound 
capable of resisting the action of the lake for “ centuries,” 
how could peat be produced under it, and how could the 
Diatomacez have lived and propagated beneath it, and much 
less the fresh-water Mollusca? It is obvious, moreover, that 
the shells of terrestrial species, accidentally mixed with the 
others, could not possibly have been drifted to such a place 
as the foundation of a heap of mould, seven feet in height 
and forty-five in diameter. I visited the locality in company 
with my friend, Mr. James MacAdam, and having examined 
the facts above mentioned, I never doubted that the tumulus 
had been raised long after the draining of the lake. Mr. Lee 
states, that ‘“ the character of the remains discovered in this 
tumulus incline us to fix the date of its formation anterior 
to the Christian era.” Tong previous to this epoch the lake 
had disappeared, and the physical conditions of the place 
* © Ulster Archeological Journal,’ May, 1858. 
