found on the coast of Northumberland and of Durham. 335 



fathoms/' It is so termed, because " in it we find the greatest 

 variety and abundance of the corneous zoophytes — arborescent 

 animals, which seem here to take the place of plants. Here we 

 find the great assemblage of carnivorous mollusca, the species of 

 Fusus, Pleurotoma, Buccinum/' &c. The fourth is the deep sea 

 Coral zone, which ranges from " fifty fathoms to beyond one hun- 

 dred :" it is " well-characterized by the abundance of the stronger 

 corals/' such as Cellepora and Oculina prolifera, ^^ by a few pe- 

 culiar Mollusca, and by peculiar Echinodermafa/' &c. 



I am not aware that there is any extensive area of sea-bottom 

 on our coasts so deep as the utmost limit here assigned to the 

 Coral zone, but there is no doubt that we have the whole of the 

 zones which have just been described. 



Had I gone over Professor Forbes's paper when mine was in 

 preparation, I should undoubtedly have given the depths of the 

 severally described species and varieties, in accordance with this 

 gentleman's views ; for it is remarkable, how strictly their vertical 

 distribution is regulated by the bathymetrical laws he has pointed 

 out. 



It will be recollected that most of the forms which I described 

 were stated to be from " deep water ;" and that I defined the 

 term in a foot-note as follows : '' By the expression ' deep water ' 

 must be understood a depth ranging from forty to eighty fathoms. 

 The greatest depth given in Norrie's chart of the North Sea for 

 the trough separating the coasts of Northumberland and Durham 

 from the Dogger and Great Fisher banks, seldom exceeds eighty 

 fathoms." Now this '' depth ranging from forty to eighty fa- 

 thoms " nearly corresponds with Professor Forbes's Coral zone. 



My former paper contained a description of " two strongly 

 marked varieties" of Ficsus antiquus : the '^ thin, short and tumid'' 

 variety I have invariably procured from the Coral zone, where it lives 

 on soft ground ; the " thick and elongated " variety inhabits hard 

 ground * in the Coralline zone : they appear to graduate into each 

 other by a form living at an intermediate depth. The thin tumid 

 variety of Fusus islandicus is also from soft ground in the Coral 

 zone ; and the " thick, long and narrow " variety belongs to the 

 Coralline zone, where it occurs on both kinds of sea-bottom. 

 Panopcea arctica, Natica groenlandica and Retepora Beaniana 

 appear to be confined to the Coral zone. The variety pelagica 

 of Mya truncata lives in the same region ; the normal variety is 

 peculiar to the Littoral and Laminarian zones ; and an interme- 

 diate form inhabits the Coralline. Fusus norvegicusj F. Turtoni f 



* The terms "hard ground" and "soft ground" are in common use 

 among the fishermen ; the former ^onx gravelli/, pebbli/, or rocky bottom, and 

 the latter for one that is muddy or sandy. 



t I regret that my paper contained no allusion to Mr. W. Bean being the 



