132 CARBONIFEROUS LAMELLIBRANCHIATA. 



hinge-line. Posteriorly the lower portion of the spaces between the ridges 

 is adorned with almost obsolete radiating ribs. 



Dimensions. — PI. VIII, fig. 4, measures — 



Antero-posteriorly . . . .49 mm. 



Dorso-ventrally (greatest at post, superior angle) . 24 mm. 

 From side to side . . . .18 mm. 



Localities. — England : Carboniferous Limestone of Settle and Bolland, 

 Yorkshire ; Castleton, Derbyshire. Ireland : Graigne, co. Limerick ; represented 

 by one poor specimen in the Geological Survey Collection, Dublin. 



Observations. — Fortunately the type specimen of Phillips's Modiola squamifera 

 is still preserved in the Gilbertson Collection in the British Museum (Natural 

 History), South Kensington, and I am permitted' by the kindness of the 

 authorities to re-tigure it (PI. VIII, fig. 5). The exposure of the hinge in two 

 specimens in the Geological Survey Museum, Jermyn Street (PL VIII, figs. 6 a 

 and 7), together with the general contour of the shell, shows that Phillips's original 

 reference of this species to Modiola was an error, and that the shell belongs to the 

 Area group ; and from the long, diverging, posterior teeth at the posterior part of 

 the hinge-plate to the genus Parallelodon, unfortunately I have been unable to 

 isolate the anterior portion of the hinge. 



The species P. Verneuilianus is the one that most closely resembles P. 

 squamifer, but it is more quadrate and less elongate, and has radiating markings 

 very highly developed all over the surface of the valves between the imbricating 

 lamellse. In P. squamifer, however, radiating markings are rarely seen, and, if 

 present, only at the extreme posterior part of the shell. This is well shown in 

 fig. 8, PL VIII, a specimen from Settle, in the Burrow Collection of the 

 Woodwardian Museum, Cambridge. It is unfortunate that no other details of the 

 interior are exposed in any of the specimens that I have been able to examine. 



This shell appears to be rare even in those localities where it does occur. 



P.uullelodon Verneuilianus, de Koninch, 1842 and 1885. Plate IX, 



figs. 13—17 a, b, c. 



Arca Verneuiliana, de Koninclc, 1842. Anim. fuss. Carb. Belgique, p. 120, 



pi. ii, fig. 12. 

 Cucull^a Verneuiliana, Bronn, 1848. Nomencl. Palaeont., p. 361. 

 Arca Verneuiliana, cVOrb., 1850. Prodrome Paleont., vol. i, p. 134. 



— — Bigsby, 1878. Thesaurus Devonico-Carboniferus, p. 299. 



Parallelodon Verneuilianus, de Koninch, 1885. Ann. Mus. Eoy. Hist. Nat. 



Belgique, vol. xi, p. 158, pi. xxiv, figs. 31 — 33. 



