184 CRETACEOUS LAMELLIBRANCHIA. 
(in 1897, see synonymy) Gallienne?, Passyi, and subinterstriatus as identical with 
P. Robinaldinus. 
The larger number of the specimens seen were obtained from the Perna-bed of 
Atherfield, the Rye Hill Sand of Warminster, the Chloritic Marl of Maiden Bradley, 
and the Cenomanian of the Devon coast. 
Affinities —This species is closely related to (and probably identical with) 
several forms described by @Orbigny, d’Archiac, ete. 
Pecten Passyi, @ Archiac,'’ from the Tourtia (Cenomanian) of Tournay, varies 
considerably, but is perhaps distinguished from P. Robinaldinus by the smaller 
intercalated ribs being more numerous and more distinct; in some cases (as in the 
type specimen) spines are absent from most of the ribs, but in other examples 
from Tournay, which I have seen, they are as numerous as in most specimens of 
P. Robinaldinus. 
P. subinterstriatus, @ Archiac,’ from the same horizon, appears to differ only in 
having very numerous ribs. 
P. Dutemplei, VOrbigny,? from the Gault, seems to be indistinguishable from 
P. Robinaldinus, except perhaps (as suggested by Pictet and Campiche) by the 
occurrence in P. Dutemplei of about fifteen ribs distributed over the whole surface 
of the anterior left ear, whereas (according to the same writers) in P. Robinaldinus 
seven or eight ribs only occur, and are confined to the lower part of the ear. But 
it 1s doubtful whether these characters are constant: im Leymerie’s figure the ribs 
seem to be distributed over the whole ear; while in d’Orbigny’s figure of P. Robinal- 
dinus the ribs, although only six in number, are also distributed over the entire ear. 
P. Galliennei, VOrbigny,* is probably only a variety with rather fewer ribs on 
the valve, and with four or five ribs distributed over the anterior left ear. It is 
recorded by Pictet and Campiche from the Upper Greensand of Ventnor. 
P. rhotomagenis, VOrbigny,’ from the Cenomanian of Rouen, is another similar 
form with numerous ribs. 
P. Oosteri, de Loriol,’ is likewise closely related to P. Robinaldinus. 
The form figured by @’Orbigny as P. interstriatus, Leymerie, 1s probably only a 
variety, but it possesses fewer ribs than any English form which I have seen. It 
approaches, however, some examples found in the Upper Greensand. 
The name aptiensis was proposed by @Orbigny (1850) for the interstriatus of 
1 <Mém. Soc. géol. de France,’ ser. 2, vol. ii (1847), p. 309, pl. xv, fig. 9. 
2 Tbid., p. 311, pl. xv, fig. 10. 
3 «Pal. France. Terr. Crét.,’ vol. iii (1847), p. 596, pl. eccexxxiii, figs. 1O—13. 
4 Thid., p. 608, pl. eccexxxvi, fizs. 5—8. 
° Ibid., p. 609, pl. cecexxxvi, figs. 9—11. 
&* Anim. Invert. Foss. Mt. Saléve’ (1861), p. 102, pl. xiii, figs. 4—8; de Loriol and Gilliéron, 
‘Urgon. infér. de Landeron’ (1869), p. 23, pl. i, fig. 18; F. J. Pictet and G. Campiche, ‘ Foss. Terr. 
Crét. Ste. Croix’ (‘ Matér. Pal. Suisse,’ ser. 5, 1870), p. 192, pl. elxx, fig. 6. 
