I 



TRANSACTIONS OF SECTION D. 703 



line, and is marliPil out by wliat I have elsewhere designated as the Mud-line. , . .' 

 ' Here is situated the great feeding ground in the ocean . . . ' and he then goes on 

 (page 1434) to enumerate the Crustaceans, such as species of Calamis, Euchceta, 

 Fasiphcea, Cranf/on, Calocaris, Pandcdus, Hippolyte, many amphipods, isopods, 

 and immense nuuibers of schizopods, which swarm, with fishes and cephalopods, 

 immediately over this mud deposit. Now I venture to think that the experience of 

 some of those who have studied the marine zoology of our own coasts does not bear out 

 this statement. In the first place, our experience in the Irish Sea is that mud may 

 be found at almost any depth, but is very varied in its nature and in its source. 

 There may even be mud laid down between tide marks in an estuary where a very 

 considerable current runs. A deposit of mud may be due to the presence of an eddy 

 or a sheltered corner in which the finer particles suspended in the water are able to 

 sink, or it may be due to the wearing away of a limestone beach, or to quantities 

 of alluvium brought down by a stream from the land, or to the presence of a sub- 

 merged bed of boulder clay, or even, in some places, to the sewage and refuse from 

 coast towns. Finally, there is the deep water mud, a very stiff blue-grey substance 

 which sets, when dried, into a firm clay, and this is, I take it, the mud of which 

 Dr. Murray writes. But in none of these cases, and certainly not in the last men- 

 tioned, is there in my experience or in that of several other naturalists I have 

 consulted, any rich fauna associated with the mud. In fact, I would regard mud 

 as supporting a comparatively poor fauna as compared with other shallow water 

 deposits. 



For practical purposes, round our own British coasts, it is still convenient to 

 make use of the zones of depth marked out by Forbes. The first of these is the 

 ' Littoral zone,' the space between tide marks, characterised by the abundance of sea- 

 weeds, belonging to the genera Lichina, Fucus, Enteromorpha, Polysiphonia, and 

 others, and by large numbers of individuals belonging to common species of 

 Balanus, Mytiiuis, Littorinn, Turpura, and Patella amongst animals. The second 

 zone is the ' Laniinarian,' which extends from low water mark to a depth of a few 

 fathoms, characterised by the abundant growth of large sea-weeds belonging to 

 the genera Laminarirr, Alaria, and Himanthalia, and by the presence of^'the 

 beautiful red seu- weeds (Floridere). Tliere is abundance of vegetable food, and 

 animals of all groups swarm in this zone, the numbers both of species and of 

 individuals being very great. The genera Helcion, Trochus, and Lacuna are 

 characteristic molluscan forms in our seas. Next comes Forbes' ' Coralline' zone 

 badly so named, extending from about ten to forty or fifty fathoms or so. Here 

 we are beyond the range of the ordinary sea- weeds, but the calcareous, coral-like 

 NulUpores are present in places in such abundance as to make up deposits coverino- 

 the floor of the sea for miles. Hydroid zoophytes and polyzoa are also abundauf, 

 and it is in this zone that we find the shell-beds lying off our coasts, produced by 

 great accumulations of species of Perf??;, Ostrea, Pectunculus, FususAud Buccinum 

 and forming rich feediug grounds for many of our larger fishes. All groups of 

 marine animals are well represented in this zone, and Antedon, Opliiothrix, Ophio- 

 f/lypha, Fdalia, In nckus, and Eurynome, maybe mentioned as characteristic' o-enera. 

 Lastly, there is what may be appropriately called the zone of deep mud (although 

 Forbes did not call it so), extending from some fifty fathoms down to (in our seas) 

 ' one hundred or so. The upper limit of this zone is Murray's mud-line. We come 

 upon it in the deep fjord-like sea-lochs on the west of Scotland, and in the Irish 

 Sea to the west of tlie Isle of Man. 



Now of these four zones, my experience is that the last — that of the deep mud 

 — has by far the poorest fauna both in species and in individuals. The mud has a 

 ptFCiiVuiv fixuna and one of great interest to the zoologist, but it is not a rich fauna. 

 It contains some rare and remarkable animals not found elsewhei-e such as Calo- 

 caris maccindreee, Patithalis oerstedi, Lipobranchius jeffreysi, Brissopsis lyrifera 

 Amphiura chiajii, Isocardia cor, and Sayartia herdmam; and a few strikino- novel- 

 ties have been described from it of late years, but we have no reason to^believe 

 that the number of these is great compared with the number of animals obtained 

 from shallower waters. 



Dr. Murray not only insists upon the abundance of arimals on the mud, and its 



