BUDLEIGH-SALTERTON PEBBLE-BED. 



363 



43. Lingula ? Hawkei, Bouault. Dav., Sil. Mom, PI. I, figs. 14 — 20 (as L. Rouaulti); 



B. S. Sup., PI. XL, fig. 21 and 27?. 



Lingula Hawkei, Bouault. Bull. Soc. Geol. de France, 2nd ser., vol. vii, p. 728, 



1850. 1 

 — Rouaulti, Salter. Quart. Journ. Geol. Soc, vol. xx, pi. xv, figs. 2, 3, 4, 



1864 ; and Dav., Sil. Mon., pi. i, figs. 14, 20, 1866. 

 Hawkei, de Tromelin. Congres de Nante?, 18/6. 

 ? — Dav. Geol. Mag., new ser., vol. vii, p. 342, pi. x, figs. 8—11, 1880. 



MM. de Tromelin and Lebesconte state, in their paper above referred to, that the shell 

 to which Mr. Salter gave the name of Ling. Rouaulti is Rouault's L. Hawkei. Mr. 

 Salter was, no doubt, as well as myself, misled by Rouault stating that his shell was 

 nearly circular, while in reality Lingula Hawkei, is marginally pear-shaped, tapering 

 considerably on the margin from about the middle to the extremity of the beak. I also 

 think he must have considered the shell I described subsequently as Lingula Salteri the 

 same; for he describes the exterior surface of his species as being covered with very fine 

 and close radiating stria?. Some remarkably well-preserved internal casts from Pontrean, 

 lent by M. Lebesconte, show a flattened 

 margin all round the inside of the edge of 

 the shell, of about one line in breadth; also 

 in the dorsal valve a deepish depression or 

 sinus (in the cast), commencing at about 

 half the length of the valve and extend- 

 ing to the inner edge of the flattened 

 margin (6), and which in the interior of 

 the valve itself must have formed an eleva- 

 tion. Two well-defined muscular impres- 

 sions occupy the central portion of the 

 valve (fig. 1, a). The surface of the in- 

 ternal cast is also finely longitudinally 

 striated ; and no doubt this is the striata, and not that on the exterior surface of the 

 valves, which M. Rouault saw and described. On the internal cast of the dorsal valve 

 the centre is occupied by V-shaped muscular scars (m and n, fig. 2), which would be the 



Lingula HawJcei, Rouault. 



1. Internal cast of ventral valve: a, muscular impression; 

 b, flattened margin. 



2. Internal cast of dorsal valve : c, muscular scars; b, flat- 

 tened margin. 



1 « 



Coquille de forme presque arrondie ; un peu plus longue que large, plus developpe'e en avant ; 

 renflee vers le liaut ; s'amincissant vers le bord, sans cotes a sa surface ; lignes d'accroissement tres marquees 

 croisc'es par d'autres longitudiuales ; fines et tres serrees. Se distingue de L. duhia, d'Orb., par sa forme pluy 

 allongee et son plus grand de'veloppement, et de L. quadrata, Eichwald, par sa largeur, qui est plus grande 

 en avant, et beaucoup moindre en venant gagner la charniere. Longeur 42 millimetres, largeur 38 milli- 

 metres, epaisseur 20 millimetres. Localite — Guichen." 



