PRODUCTUS. 1G1 



the curves of the opposite one, and similarly ornamented. Interior unknown. A British 

 specimen measured — length 9^, width 11, lines. 



Obs. 1 am acquainted with but a single British example of this species, stated to have 

 been found in Carboniferous limestone north of Glasgow (?) and now preserved in 

 the museum of Practical Geology. The identification is given on the authority of 

 Prof, de Koninck, and it would be very desirable that more specimens should be obtained 

 and examined before its specific claims be definitely recognised. Our Scottish example 

 agrees, however, very nearly with the figure published by Prof, de Koninck of a specimen 

 found in a calcareous nodule at Chokier, in Belgium, and M. de Verneuil states he has ob- 

 tained the species in a Carboniferous limestone in the valley of Prikcha (Valdai), Russia. 



Productus undatus, Defiance. PI. XXXIV, figs. 7 — 13. 



Productus undatus, Def ranee. Die. des Sc. nat, vol. xliii, p. 354, 1826. 



— — De Koninck. Desc. des Aniniaux fo.*s. du Terrain Carb. de 



Belgique, p. 156, pi. xii, fig. 2, 1843; and Mon. du genre 

 Productus, pi. v, fig. 3. 



— TORTiLis,ilf'Coy. Synopsis of theCarb.Foss. of Ireland, tab. xx, fig. 14, 1844. 



— undatus, Be Verneuil. Russia and the Ural Mountains, vol. ii, p. 261, 



pi. xv, fig. 15, 1843. 



— — Day. Mon. Scottish Carb. Brach., p. 41, pi. iv, figs. 15 — 17, 



1860. 



Spec. Char. Shell somewhat sub-orbicular or slightly transverse ; hinge-line rather less 

 than the width of the shell. Ventral valve regularly vaulted, very convex, without sinus ; 

 beak small, rounded, incurved, not extending much beyond the hinge-line ; auriculate ex- 

 pansions small. Surface covered with numerous irregular or interrupted sub-parallel, un- 

 dulating, concentric folds or wrinkles, which become wider and more produced with age, 

 and having their narrow, almost perpendicular, side directed towards the beak ; the valve is, 

 moreover, ornamented by numerous minute, rounded, thread-like striae, separated by narrow 

 sulci, and of which from five to six may be counted in the thickness of a line, and 

 swelling out at intervals, they give rise to a slender spine. Dorsal valve concave, following 

 the curves of the opposite one, and similarly ornamented. Interior unknown. Dimensions 

 variable ; two British examples have measured — 

 Length 14, width 13, lines. 

 19 i q 



Obs. This remarkable species, although not common, is by no means very rare in the 

 Carboniferous limestone of Great Britain, and may be easily distinguished from other 

 British Producta by that curious terrace-shaped or crumpled-like appearance it presents, 

 and which is caused by the numerous concentric wrinkles which cover the surface of both 



21 



