GASTRIOCERAS CIRCUMNODOSUM. L99 



of Oastrioceras Listeri, G. carbonarium, and G. coronatum. These were all very 

 serviceable for comparison with the Firoda specimens. I am much indebted also to 

 Dr. Wheel ton Hind, who sent me, from his large collection of British Carboniferous 

 Fossils, specimens of G. Listeri and G. carbonarium in different stages of growth. 

 Thus I had ample material for the study of the present species in its relationship 

 with those above named. 



Before concluding' the description of this species it may not be out of place to 

 refer briefly to the history of Gastrioceras Listeri. The chief interest of this centres 

 in the question, which I had the opportunity lately of discussing with Dr. Hind, as 

 to whether the species figured by Martin (1809) under the name "Ammonites 

 Listeri " is the same species as the one afterwards figured by J. de C. Sowerby 

 (1825) under the same name. The specimen figured by Martin is lost, therefore 

 only the description and figure are available as evidence ; the latter is decidedly 

 unsatisfactory, and would only represent very roughly the characters of the 

 ornamentation of the shell now known as Gastrioceras Listeri. 



Another difficulty is that Martin always describes his species as occurring " in 

 limestone tracts," and associates it with the species (of many of which he was 

 himself the author) commonly occurring in, and characteristic of, the Mountain 

 Limestone. It is well known that Gastrioceras Listeri, as universally recognised, 

 belongs to formations of higher horizons than the latter, extending upwards to the 

 Coal Measures. 



Therefore, if Martin's name Listeri is still to be employed, it must be with the 

 understanding that he was in error as to the horizon of his species. Though it is 

 impossible to ascertain the exact locality whence Martin obtained his figured 

 specimen and others — for he recognised the species as common,— the locality he 

 vaguely referred to as " near By em [or By am] and Middle ton " must have included 

 rocks other than the Mountain Limestone, because, according to all experience, 

 G. Listeri is not found at so low an horizon. It seems in the highest degree 

 probable that the conjecture as to the stratigraphical origin of Martin's figured 

 specimen quoted in the foot-note below is correct. 1 



In concluding these observations I may draw attention to a point which, how- 

 ever trifling it may seem, is worthy of note, namely, that in the hand-colouring of 

 Martin's figure gold has been used to represent iron pyrites, a mineral of common 



1 Dr. Wheelton Hind, with characteristic enthusiasm, made a journev to Eyam and Middleton in 

 April of this year (190:}) to find out. what, rocks occur at those places, and he wrote to me giving me a 

 sketch of the section there, showing the Mountain Limestone and the Pendleside Series in connection 

 with it. "The Pendleside Series," he said, " contains thin Mack limestones in which G. Listeri occurs 

 at other localities, so that it is probable the specimens [Martin's] were obtained from these beds, 

 which were extensively worked in past years for lead veins which traversed them. These beds are 

 above the Yorcdale Series of Wenleysdale, in which Q, Listeri lias never je\ been found.'' 



