E. Etheridge, jun. — On the genus Conularia. 295 



It may be said that the volcanic or trap rocks appear to have 

 effected very little disturbance in the rocks through which they have 

 risen; violent disturbance and horizontal compression, as well as 

 elevation and metamorphism, being confined almost wholly to the 

 extrusion of the massive and highly crystalline rocks which are 

 usually distinguished as 'Plutonic,' viz. the granites, porphyries, 

 serpentines, etc., etc. This is, however, exactly what might be 

 expected on. the supposition that the upthrust of the latter is the 

 direct effect of their subterranean expansion from increase of heat; 

 the rise of the former, the secondary effect of these movements, due 

 to the opening of lateral fissures, often at a considerable distance 

 from the axis or centre of elevation, affording issue to portions of 

 the heated interior suddenly relieved from pressure. 



Such lateral fissures being almost necessarily parallel to the axes 

 of elevation, we may see here the cause of the general parallelism 

 of lines of volcanic eruption to the neighbouring continental 

 mountain ranges, as well as of their. frequent coincidence with coast- 

 lines, that is, with the edges of the up-raised areas.' 



This view of the subject, I believe, corresponds more nearly with 

 that advocated by Captain Hutton, in his New Zealand lecture, than 

 with that of Mr. Fisher, who looks for his original cause of change 

 in the assumed contraction of the earth's nucleus within a more or 

 less rigid crust. 



III. — Contributions to Cakboniferous Paleontology. 



By E. Etheridge, Junior, F.G.S., of the Geological Survey of Scotland. 



I. — Note on the genus Conularia, Miller. 



THE genus Conularia was first described by Miller about the year 

 1820, and afterwards more fully by Sowerby, as a " conical 

 hollow univalve shell," (Min. Con., vol. iii. p. 107). It had pre- 

 viously been figured by Ure under the name of a "curious fossil" 

 (History of Euthergien and E. Kilbride, p. 330). Sowerby, amongst 

 other characters, noticed that in one of his specimens, formerly in 

 Miller's collection, the edges or " lips " of the broader or truncated 

 end of the shell were inflected, and nearly met in the centre (1. c. t. 

 260, fig. 4). 



1 



Conularia quadrisulcata, Sby. Upper Limestone (Carboniferous) 

 series. Williamwood near Glasgow. 



The specimen in question appears to have been in a very muti- 

 lated and crushed condition, and if we are to judge from Sowerby's 

 ^ See Volcanos, pp. 275-287, ed. 1872. 



