184 CRETACEOUS LAMELIJBRANCHIA. 



(in 1897, see sjnoiivmy) nollicvnci, Pasi<yi, and sahintcrsfriatiis as identical witli 

 P. B.ohinnldinns. 



The larger nnmber of the specimens seen were obtained from the Fcrna-heiX 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 prol)al)ly identical with) 

 several forms described by d'Orbigny, d'Archiac, etc. 



Peden Passyi, d'Archiac,^ from the Tourtia (Cenomanian) of Tonrna}', varies 

 considerably, bnt is perhaps distinguished from P. Rohlnaldinus by the smaller 

 intercalated ribs being more numerous and more distinct ; jn 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. Bohinaldinus. 



P. suhlnterstriatus, d'Archiac," from the same horizon, appears to differ only in 

 having very numerous ribs. 



P. Diitemplei, d'Orbigny,^ from the Gault, seems to l)e indistinguishable from 

 P. Eohinaldinus, except perhaps (as suggested by Pictet and Campiche) by the 

 occurrence in P. Butemplei of about fifteen ribs distributed over the whole surface 

 of the anterior left ear, Avhereas (according to the same writers) in P. Boh in aid 171 n,s 

 seven or eight ribs only occur, and are confined to the lower part of the ear. But 

 it is doubtful whether these characters are constant : in Leymerie's figure the ribs 

 seem to be distributed over the whole ear; while in d'Orbigny 's figure of P. Bohinal- 

 dinus the ribs, although only six in number, are also distributed over the entire ear. 



P. GaUiemici, d'Orbigny,'* 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. rJiotomagenis, d'Orbigny,'" from the Cenomanian of Rouen, is another similar 

 form with numerous ribs. 



P. Oosteri, de Loriol,*^ is likewise closely related to P. Bohinaldinus. 



The form figured by d'Orbigny as P. inter sfriatus, Leymerie, is probably only a 

 variety, but it possesses fewer i-ibs than any English form which I have seen. It 

 approaches, however, some examples found in the Upper Grreensand. 



The name aptiensis was proposed by d'Orbigny (1850) for the intcrstriatus of 



1 ' Mem. Soc. geol. de France,' ser. 2, vol. ii (1847), p. 309, pi. xv, fi<?. 9. 



2 Ibid., p. 311, pi. XV, fig. 10. 



■■5 'Pal. Fran?. Terr. Cret.,' vol. iii (1847), p. 596, pi. ccccxxxiii, figs. 10—13. 



4 Ibid., p. 608, pi. ccccxxxvi, fi-s, 5—8. 



■> Ibid., p. 609, pi. ccccxxxvi, figs. 9—11. 



c ' Anim. Invert. Foss. Mt. Salove ' (1861), p. 102, \y\. xiii, figs. 4 — 8; dc Loriol and Grillii'roii^ 

 ' Urgon. infer, de Landeron ' (1869), p. 23, pi. i, fig. 18 ; F. J. Pictet and G. Cami)iche, ' Foss. Terr. 

 Cret. Stc. Croix' (' Mater. Pal. Suisse,' ser. 5, 1870), y. 192, pi. clxx, fig. 6. 



