206 C. T. Trechmann and D. Woolacott — 



One of my specimens measures 2 mm. in length and slightly over 

 1 *5 mm. in height ; another is 3 mm. long and 2 mm. high. 



Kirkby wisely declined to arrive at any definite decision as to the 

 real nature of this organism and stated clearly his reasons both for 

 and against regarding it as an Ancylus, a Biscina, an JEstheria, or 

 a bivalve mollusc. 



Some later geologists have, however, adopted a less cautious 

 attitude, and Dr. Wheelton Hind has definitely described and figured 

 specimens from Claxheugh as a lamellibranch, calling them 

 Carbonicola Vinti} Carhonicola is a genus which bears hinge-teeth. 



X D.W. 



Fig. 2. — Section at XY in Fig. 1. (Enlarged.) 



Sh. Shale with fossiliferous ironstone bands, slightly faulted along XY ; 

 the fault dies out in the upper beds. 



C. A band of slickensided clay and broken shale (1J in. thick), which on 

 the west of the section runs along the top of the ironstone band beneath the 

 sandy shale, but is not faulted by IT, being continued straight on in the bed 

 of shale. This layer lies along a thrust-plane. 



1. Light-coloured argillaceous sandstone. 



2. Thinly bedded sandy micaceous shale. 



He regards the Claxheugh specimens as "the closely compressed 

 remains of the periostracum of a large number of shells". My 

 examination of a large series of specimens, however, reveals 

 difficulties in accepting this view. They show no trace of calcareous 

 matter and seem to have consisted entirely of chitinous material, but 

 on the same slab one observes numerous valves of Anthracomya, and 

 of small entomostraca still retaining their calcareous nature, so that 

 it is not easy to believe that the valves of " Carhonicola" Vinti have 

 become decalcified, while those of other equally delicate calcareous 

 organisms have remained unaffected. The Claxheugh specimens are 

 clearly not-shells which have been partly decomposed or decalcified. 

 However, a speaker at the discussion on the above-mentioned 

 paper assumed that the bivalve nature of the fossil was decided. It 

 is clear to me from examination of my specimens that the organism 



1 ' ' On three New Species of Lamellibranchs from the Carboniferous Eocks 

 of Great Britain " : Q.J.G.S., vol. lv, p. 365, 1899. 



