CHONETES. L88 



a pseudo-deltidium, the cardinal process of the opposite valve filling up the remaining 

 open space. Surface of both valves covered with numerous fine, thread-like, straight or 

 flexuous striae, which become more numerous by means of bifurcation and intcrstriation 

 at variable distances from the beak and umbo, the striae and interspaces being closely 

 crossed by numerous line, concentric lines of growth, which produce a beautifully crenu- 

 lated appearance. Small spines rise from the striae at variable distances, and a row of 

 from twenty to thirty short ones project from the cardinal edge. Valves strongly articu- 

 lated by means of teeth and sockets. Interior details imperfectly known. Dimensions 

 variable j two British examples have measured — 



Length 2 inches, breadth 5 inches 3 lines, greatest width between the valves 3 lines. 

 1 19 li 



Obx. This is perhaps the largest and most beautiful species of the sub-genus 

 hitherto discovered, and is remarkable on account of its elegant shape and sculpture. 

 C. comoides is the only species with which the shell under description might be compared, 

 but from which it can be distinguished without much difficulty, C. comoides being a 

 much more ponderous and gibbous shell, and whose beak appears to be generally more 

 rounded and produced than is that of C. papilionacea . Although it received the very 

 appropriate name of papilionacea from Phillips in 1836, it had been figured and shortly 

 described by Lister in 1G88 — "Pectinites flabelliformis tuberculoso commissura seu 

 pectinites semicircidaris compresso minuta ad modum striatus." 



C. multidentata, M'Coy, of which I have been able to examine the original specimen, is 

 evidently a synonym of the shell under description, and I am inclined to believe that the 

 fragment figured and described by the same author under the denomination of C. papyracea 

 is also another synonym. In England C. papilionacea has been found in the Carboniferous 

 limestone of Bolland, Otterburn, Kendal, Settle, Ronalds Way, Isle of Man, and 

 Dalton, in Furness, Lancashire, &c. In Ireland at St. John's Point, Ballybodonnel, 

 Dunkineely ; Cheeverstown, County Dublin, &c. On the Continent it has been found 

 by Prof, de Koninck in the Carboniferous limestone of Vise, Chokier, and Temploux, 

 in Belgium ; Karova, Government of Kalougarear, Moscou ; and at Sable, in France. 



Chonetes Dalmaniana, De Koninck. PI. XLV1, fig. 7 . 



Chonetes Dalmaniana, Be Kon. Desc. des Animaux foss. du Terrain Carb. de 



Belgique, pi. xiii, fig. 3; pi. xiii bis , fig. 2, 1843; and 

 Mon. du genre Chonetes, pi. xix, fig. 3, 1847. 



Spec. Char. Shell thin, transversely semicircular, concavo-convex ; hinge-line as wide 

 as the greatest breadth of the shell. Ventral valve regularly, but moderately, convex ; area 

 narrow, sub-parallel, and divided in the middle by a small fissure, partly arched over by a 

 pseudo-deltidium. Dorsal valve concave, following the curves of the opposite one ; area 



