TRANSACTIONS OF THE SECTIONS. 73 
animal. There appears to be some relation between the structure and composition 
of the spines and the habits of this species; they are generally well-developed in 
proportion to its size, and sections of them, viewed under the microscope, present 
appearances of greater strength and density than similar preparations of the spines 
of Echinus sphera, though a much larger species. The following are the results of 
a chemical examination made, at my request, by Mr. J. W. Smyth, assistant in the 
laboratory of Queen’s College. 
Echinus sphera. Echinus lividus. 
Specific gravity ...... 2°49 2°55 
Inorganic matter ..... 82°03 per cent. 82°26 per cent. 
Organic matter ...... 17°97 per cent. 15‘74 per cent. 
Pens aeotn ot ncievae's to spat o)2e Chiefly carb. of lime. | Chiefly carb. of lime. 
‘Siluie Soe peat bee SR Laie » + | 0°05 per cent. 0°41 per cent. 
list has See ne chee ane none. a trace. 
The smaller proportion of organic matter, and greater amount of inorganic gene- 
rally, and of silica in particular, appear to indicate some relation between the spines 
of Lchinus lividus and its burrowing powers. The spines on the sides and lower 
surface of the animal are generally abraded, particularly in immature individuals ; 
when it has attained full size, and the cavity completed, the spines are often, if not 
always reproduced. By actual experiment, I have proved that the spines are capable 
of abrading rock of moderate hardness. 

On a New Map of the Geological Distribution of Marine Life, and on the 
Homoiozoic Belts. By Professor Epowarp Forsss, £.R.S. 
On this map the provinces under which animals and vegetables are assembled, are 
delineated so as to show their peculiarities, relations, and contrasts. The character of 
each is marked by the entire assemblage of organized beings constituting its popu- 
lation ; a considerable portion in most cases being peculiar, and a still larger number 
ora ee. 
it. 
ou 
7 
of species having their areas of maximum development within it. The several prfo- 
vinces vary greatly in extent, some being very stall, some very large. But though 
Hot equally important ih a geographical point of view, their inequality of extension is 
not opposed to their being of equal natural history importance. The author showed 
that the northern and southern limits of each province correspond with the boundaries 
of a latitudinal belt,to which, on account of the similarity of organic features presented 
throtighout its extension, the name of Homoiozoic is proposed to be applied. Nine 
of these belts are distinguished; of which one is unique, central, and equatorial, and 
four in the northern hemisphere represent as many in the southern. The boundaries 
of these belts on land appear to correspond with the isotherm of the months in which 
there is the greatest vivacity of animal and vegetable life. The homoiozoic belts are 
not of equal breadth in all parts ; and whilst the Polar belts include only a single pro- 
vince in each, the others severally include many provinces. On the same map, the 
comparative distribution of marine life in zones of depth in different and distant re- 
gions is also laid down, and a nomenclature applicable to all seas is proposed for 
them. 
Remarks on a species of Sepiola new to Britain, and first procured in the 
_ Neighbourhood of Belfast. By Professor Epwarp Forsrs, F.R.S. 
One species only has hitherto been recognised in the British seas, and this has always 
been identified by our naturalists with the common Sepiola of the Mediterranean. Ger- 
vais andVan Beneden, in 1838, maintained that the Sepiola of the Atlantic coasts of 
Europewas different from that inhabiting the Mediterranean. The distinctions indicated 
by them, however, were quite insufficient to warrant the inference drawn by these ob- 
servers. M. A. D’Orbigny was the first to determine a true and important difference, 
but likewise committed the error of supposing that all the Atlantic individuals were 
of one type and the Mediterranean ones of another. He consequently referred all the 
