AIR-BREATHERS OP THE COAL PERIOD. 279> 



the genus Pupa, that I have not thought it desirable to refer it to 

 a different genus, though the name Dendropupa has been proposed 

 by Prof. Owen. Mr. J. S. Jeffreys and other eminent concholo- 

 gists, who have seen the shell, concur in the opinion that it is a 

 true Pupa ; so that this genus, like Lingula and Nautilus, extends 

 from the palaeozoic to the modern times. 



It may be described as a cylindrical shell, tapering to the apex, 

 with a shining surface, marked with longitudinal rounded ridges. 

 The whorls are eight or nine, rounded, and the width of each 

 whorl is about half the diameter of the shell. The aperture is 

 rather longer than broad ; but is usually somewhat distorted by 

 pressure. The margin of the lip is somewhat regularly rounded 

 and is reflected outward. There are no teeth, but a slight indica- 

 tion of a ridge or ridges on the pillar lip, which may however be 

 accidental. Length T 3 7 ths of an inch or a little more. It wa3 

 first recognized by Dr. Gould of Boston, in specimens obtained by 

 Sir C. Lyell and the writer at the Joggins. 



This little shell is remarkable, not merely for its great antiquity, 

 but also because it is separated by so wide an interval of time 

 from any other known species of its race, there being no other 

 Pulmonate known until we reach the Purbeck beds, and no true 

 land snail until we reach the Tertiary. It is also worthy of remark,. 

 that while hundreds of specimens have been found, not only in 

 the erect reptiliferous trunks but in a bed 121V feet lower, and 

 separated by twenty-one coal beds, not any other species is found 

 with it. It is very rare in modern times thus to find one species of 

 snail in great abundance without any others. More especially is 

 this so when we can examine, as in this case, not only the decayed 

 trunks in which the creature sheltered itself, but also the beds of 

 mud into which its dead shells were washed. These facts present a 

 striking instance either of that ''imperfection of the geological 

 record", of which we hear so much, or of the solitary existence of 

 a single species as a prophetic representative of future things, to 

 be realized long after it had ceased to exist. 



The lower bed, holding shells of Pupa vetusta, just mentioned, 

 is a grey and greyish-blue under-clay, full of stigmarian rootlets, 

 though without any coal or erect trees at its surface. It is 7 feet 

 thick, with sandstone above and below. The shells occur very 

 abundantly in a thickness of about two inches. They have been 

 imbedded entire; but most of them have been crushed and flat- 

 tened by pressure. They occur in all stages of growth ; the young 



