280 APPENDIX TO THE SUPPLEMENTS TO 



CARBONIFEROUS. 



1. Cuonetes Laguessiana, de Koninck. Dav., Garb. Mori., p. 186, PI. XLVII, figs. 



12— 1G, 17, and 18 ; Dav., Carb. Suppl, 

 p. 312, PL XXXIV, fig. IS ; Dav., Appen- 

 dix to Supplements, Vol. V, PI. XX, figs. 

 20 20, a, b, 21, 21 a. 



This well-known species has been described and illustrated in my ' Carboniferous 

 Monograph ' and its Supplement, but its intimate shell-structure had not then been 

 investigated. 



It has been said by Dr. Carpenter at p. 37 of his chapter on the intimate structure of 

 the Brachiopoda, forming part of the General Introduction to Vol. I of my ' British 

 Fossil Brachiopoda : ' " Chonetes, of this genus also, I have examined two species, 

 armata and lata, both of which are perforated;" but Dr. Carpenter does not explain in 

 what way they are perforated, namely, whether the perforations pass through the entire 

 thickness of the valves or are restricted to certain portions of it, as was shown by Mr. 

 John Young to be the case in the genus Productus (' Carb. Suppl.' pp. 295 — 302). I 

 therefore suggested to my valued friend, Mr. J. Young, that he should examine with 

 care the shell-structure of Chonetes Laguessiana, which occurs abundantly and in an 

 excellent state of preservation in the Carboniferous Shales at Capelrig Quarry and other 

 places in Lanarkshire. Mr. Young kindly complied with my solicitations, and also at 

 my request published his observations in the ' Geol. Mag.' Decade 2, vol. x, p. 368, 

 August, 1883. Mr. Young found that, as in Productus, the shell of Chonetes is not 

 perforated through its entire thickness, and I cannot do better than to reproduce here 

 some of his statements. 



" When we examine the outer surface of the shell of this Chonetes, in well-preserved 

 specimens, we find that the numerous ribs are comparatively smooth, and that in most 

 specimens they are crossed by a few concentric lines of growth, which are generally 

 placed near the outer margin of the valves. The ribs are also perforated to a certain depth 

 and at irregular intervals, by a slanting series of tubular openings, that were probably 

 occupied by the bases of small spines. They are variable in number, on the average 

 from eight to ten in the length of each rib. If the outer surface of such a specimen is 

 slightly etched with weak acid, so as to remove a thin film of the shell, we then see that 

 each rib is ornamented with a single row of very minute and closely-set tubercle-like 

 pores, that descend vertically for a short distance into the substance of the shell, and 

 then disappear as the surface is etched a little deeper [PI. XX, figs. 21 and 2 1 a]. Whether 

 these minute perforations ever opened at the surface of the shell as pores, it would now 



