THE BRITISH FOSSIL BRACHIOPODA. 283 



themselves until he came close to the inner layer of the valves where they appear in the 

 shell-structure as a series of little greyish-white tubes, slanting upwards towards the beak 

 of the shell, as is seen in Chonetes Loguessiana. 



In his paper " Ueber die Fossilien der Schlesischen Kohlenkalkes " (' Dentschen 

 Geologischen Gesellschaft Jahrg.,' 1854), P. v. Semenow figured a magnified portion 

 of the shell of Chonetes hemispharica, showing large perforations between the ribs and 

 minute punctures on the ribs, similar to all appearance to what was found by Mr. 

 J. Young to be the case with C. Laguissiana. These, however, do not traverse the whole 

 thickness of the valve. 



Genus — Aulacorhynchus, Dittmar, 1871. 1 



= Genus Isoyramma, Meek, 18/3. 2 



2. Aulacorhynchus Davidsoni, Barrois. Dav., Carb. Mon., PL LV, fig. 13; Dav., 



Appendix to Supplements, Vol. V, PL 

 XX, fig. 22. 



Chonetes concentrica, Dav. Carb. Mon., p. 2/8, pi. lv, fig. 13 (not C. concentricu, 



de Koninck). 

 Aulacokhynchus Davidsoni, Barrois. Recherches sur les terrains Anciens des 



Asturies, et de la Galice, Memoires Soc. 



geol. du Nord., vol. iii, p. 326, pi. xvi, 



fig. 6, 1882. 



At p. 278 of my ' Carboniferous Monograph ' I described and figured a large semi- 

 circular shell that had been obtained from the Carboniferous Limestone at Kenness 

 Wood, Kinross, in Scotland, and referred it with much uncertainty to the Chonetes 

 concentrica, de Kon., after having previously consulted my Belgian friend upon the 

 subject. Since then Dr. C. Barrois has given the specific name of Aulacorhynchus 

 Davidsoni to the shell I had referred to Chonetes concentrica, having found similar 

 examples in great abundance in the Carboniferous Limestone of Villayana, Onis, 

 Villanueva, and Pola de Leila, in the Asturies. It differs from de Koninck's C. concen- 

 trica by its much larger dimensions as well as by its more numerous and comparatively 

 smaller concentric ridges. 



In 1854 Dittmar described three allied species under the generic name of Aula- 



1 ' Ueber ein neues Brachiopoder-Geschlecht aus dem Bergkalk ;' K. Akad. Wiss. St.-Petersburg, 

 1871. 



2 'Geol. Survey of Illinois,' vol. v, p. 568, 1873. 



38 



