TRANSACTIONS OF SECTION C. 493 
fresh water. Megalichthys and Pleurodus are fishes which in the coal measures 
probably lived in fresh or brackish water; and though they may have been adapted 
to exist in marine conditions, the occurrence of beds of sand and shale intercalated 
with the thin limestones of the Yoredales evidently shows the proximity of land, 
and it is probable that they were carried to their present position by rivers and 
there deposited with the marine forms with which they are associated. The sup- 
position that the water was brackish may account for the small size of some of the 
genera already mentioned, and their final extinction in the grits and shales which 
succeed the limestone. The great fishes whose remains are found in the lower 
limestone, represented by Ctenacanthus, Oracanthus, and others, are absent, the only 
spines hereto found being those of Cladacanthus and Physonemus. 
FRIDAY, SEPTEMBER 21. 
The following Reports and Papers were read :— 
1. Eleventh Report on the Erratic Blocks of England, Wales, and Treland. 
See Reports, p. 136. 
2. On some supposed Fossil Algce from Carboniferous Rocks. 
By Professor W. C. Wituiamson, LL.D., F.R.S. 
During past years many objects have been figured and described by authors 
under various names, but all of which have been regarded by some paleontologists 
as Fucoids. One very curious group especially, obtained from the pre-carboni- 
ferous rocks, has been described under such names as Bilobites, Chrossochorda, 
&e. The Rey. Isidore Kavannah, a young alumnus of Stonyhurst College, near 
Whalley, about a year ago placed in the author’s hands a number of specimens 
which he had found in Yoredale rocks on the banks of the Hodder, near the college. 
These specimens would be considered by those who believe in the vegetable nature 
. of such examples to belong to the genus Chrossochorda. M. Nathorst has recently 
given excellent reasons for regarding all such specimens as being merely the casts 
of the depressed tracks of Crustaceans, worms, and other animals, and in plate 1, 
fig. 1 of his memoir’ he has figured one formed by the crustacean Corophium 
Jongicorne, which, in its essential features, corresponds with the various Chrosso- 
chord. Hitherto none of these litter objects have been found in the carboniferous 
rocks; but since the author received the Stonyhurst specimens Mr. Robert Kidson, 
of Stirling, has figured one from the Carboniferous beds of Liddlesdale, under the 
name of Chrossochorda carbonaria. In his specimens the pennatiform ridges given 
off obliquely from the central longitudinal furrow are smooth. In the author’s 
specimens they are markedly muricated or regularly tuberculated. Whilst wholly 
rejecting the idea of these objects being other than the casts of animal tracts, these 
specimens may be known provisionally as Chrossochorda tuberculata. 
A number of casts strikingly representing branching alge were made on a 
smooth sandbank at Llanfairfechan, in North Wales, where drainage channels 
left by each retiring tide resembled in a most remarkable manner some of the 
objects described as fossil Algee. Specimens of these casts were exhibited. 
3. Report on the Fossil Plants of Halifax.—See Reports, p. 160. 
1 Om Spér af ndgra evertebrerade djur M. M. Och Deras Paleontologisha Bety- 
delse. A.G, Nathorst. Stockholm, 1881. 
