168 BRITISH CARBONIFEROUS BRACHIOPODA. 



and elongated appearance, its ribs being likewise more numerous and regular, both in 

 the young and adult condition, than what is usually observable in Martin's species. In 

 this opinion I am supported by Prof, de Koninck and Mr. Young, but am still some- 

 what uncertain whether the shell under description is in reality more than a variety of 

 Martin's species. 



In Scotland, P. Youngianus occurs abundantly in a white friable shale above ;t 

 coralline bed {Lithodendron fasciculatum, Fleming, Lithostrotion Martini, M. Edwards). 

 It is found also at Brockley, near Lesmahago, in Lanarkshire, as well as in Renfrew- 

 shire, Ayrshire, and Fifeshire. 



In England in Carboniferous limestone at Llangollen, in Wales. 



Productus pustulosus, Phillips. PI. XLI, figs. 1 — 6 ; PI. XLII, figs. 1 — 4. 



Pyxis transversim striata, Chemnitz. Martini's Neues Syst. Conch. Cabinet, 



vol. vii, p. 301, pi. lxiii, figs. 605 and 606, and 

 vol. viii, fig. 69, 1784. 



Producta pustulosa, Phillips. Geol. of Yorks., vol. ii, p. vii, fig. 15, 1836. 



— rugata, Phillips. lb., fig. 16. 



— ovalis, Phillips. lb., pi. viii, fig. 14. 



Productus pustulosus, De Koninck. Desc. des Anim. foss. du Terr. Carb. de 



Belgique, pi. xii ,)is > fig. 3, 1843. 



— punctatus, Kon. (non Martin). lb., pi. ix, fig. 6. 



— pustulosus, Kon. Mon. du genre Productus, pi. xiii, fig. 1, and pi. xvi, 



figs. 8, 9, 1847. 



— pyxidiformis, Kon. lb., pi. xi, fig. 7 ; pi. xii, fig. 1 ; pi. xvi, fig. 2. 



Spec. Char. Shell thin, rotundato-quadrate, wider than long, rarely oval and longer 

 than wide ; hinge-line shorter than the greatest width of the shell. Ventral valve regu- 

 larly arched and gibbous, divided longitudinally by a sinus of greater or lesser depth and 

 width ; beak moderately developed and incurved, not overlying the hinge-line except at 

 its attenuated extremity ; ears wide, nearly rectangular, and flattened ; margin slightly 

 indented in front. External sculpture varying somewhat in appearance in different speci- 

 mens, but usually covered with numerous continuous or interrupted transverse, undulating 

 wrinkles, while numerous pustules or elongated tubercules, bearing slender, tubular spines, 

 are subquincuncially arranged or disposed in irregular rows over the entire surface. Dorsal 

 valve slightly concave, with a small mesial elevation or fold, while numerous transverse 

 wrinkles, tubercule-pits, and short spines, cover the surface. Dimensions variable ; three 

 examples measured — 



Length 44, width 46, greatest depth between valves 17, lines. 



JJ W ^J JJ "^J JJ JJ JJ -*■"> JJ 



J> •" Z *J JJ *"l JJ J> JJ O, ,, 



06s. After a lengthened comparison and study of more than one hundred specimens 



