534 



THE GEOLOGIST. 



inferred from other data— perhaps chiefly from the nature of the animals of the 

 coal-measures. I will only say that there are in the neighbourhood of Man- 

 chester instances of thick beds of coal, overlaid immediately by uniform fine 

 shale (without a particle of grit or sand which might indicate a subsidence of 

 the surface), which shales contain only marine shells. The majority^ of the 

 shells, however, of the middle and upper coal-measures are not so decisive of 

 their habitat, and I wish now to call attention to some of these. 



Fig. . 



The so-called " Unto" bands of the coal-measures are so well known as not 

 to need description. In the condition of broad banks often several feet thick, they 

 occur throughout all our fields : and though rare in the lower measures, they 

 are not absent from them. A number of species have been described, some 

 of them probably the merest varieties of the three or four well-marked forms 

 originally described by So werby in the "Mineral Conchology." But others 

 arc distinct forms, and some yet remain to be distinguished and added to our 

 lists. Some speeies appeal- to be characteristic of particular seams or bands 

 in the coal, and to be almost confined to these ; others, as the common JJnio 

 a cut us, arc found even so far down as the mountain limestone shale, and lived 

 on to the close of the coal period with a wide geographical range. 



They have been distinguished from the Unio of our freshwater lakes and 

 rivers by Prof. King, and though it is as yet by no means certain that they are 

 allied to the Myculcc, the character of their epidermis, and the internal position 

 of the ligament that binds the shells together, leads to the belief that they 

 were marine shells. 



dntkmeosid*— They are thick shells, and yet destitute of hinge-teeth. The 



