PECTEN. 201 



It is difficult to separate Janira Johannis Boehmi, Tiessen, 1 from /'. (N.) cometa, 

 since in the latter the symmetry (depending' on the position of the middle rib) 

 varies in different specimens. 



P. (Neithca) cometa also presents some resemblance to the smaller forms of 

 P. (N.) atavus, but is distinguished by possessing five (instead of six) main ribs, 

 by being relatively higher, and by having the right valve more convex. 



Remarks. — This appears to be a relatively rare species. A specimen from the 

 Oenomanian of Saint Jouin (Seine-Inferieure) has been sent me by M. Fortin, and 

 agrees perfectly with the English examples. 



Types. — D'Orbigny's specimens came from the Ceiiomanian of Villers (Calva- 

 dos) and Le Havre (Seine-Inferieure). 



Distribution. — Upper Greensand (zone of Pecten asper) of the Isle of Wight, 

 Maiden Bradley, Melcombe Bingham (Dorset), south-west of Armswell Farm 

 (Dorset), and west of Melbury Hill (Dorset). Rye Hill Sands of Warminster. 

 Chloritic Marl of Ventnor and Maiden Bradley. Ceiiomanian of Wilmington. 



Pecten (Neitiiua) Morrisi {Pictet awl Benevier), 1858. Plate XXXIX, figs. 



11a— c, 12a, b, 13. 



? 1841. Pecten quinquecostatus, var. a, F. A. Bomer. Die Verstein. d. nord- 



deutsch. Ereidegeb., p. 51. 



1845. — E. Forbes. Quart, Journ. Geol. Soc, vol. i, 



p. 249 (partint). 



1846. versicostatus, A. Leymerie. Statist, geol. et inin. du depart, de 



l'Aube, Atlas, p. 11, pi. vi, fig. 9. 



1847. — quinquecostatus, var., /. Morris. Quart. Journ. Geol. Soc, 



vol. iii, p. 295 (foot-note). 

 1853. Janira ^uinquecostata, F. J. Pictet and W. Boux. Moll. Fuss. Gits verts 



de Geneve, p. 506, pi. xlv, 

 figs. 3 a, b (not c). 

 1858. — Mokrisi, F. J. Pictet and E. Beneoier. Fuss. Terr. Aptien (Mater. 



Pal. Suisse, ser.l), p. 128, 

 pi. xix, fig. 2. 

 ? 1859. QUiNyuEcosTATA, J. Vila nova y Pivra . Mem. geogn.-agric. de Cas- 



fcellon, pi. iii, fig. 23. 

 1865. Mokbisi, E. Coqnand. Mon Aptien del'Espagne, p. 151. 



1870. — F. J. Pictet and G. Campiche. Foss. Terr. Cret. Sir 



Croix (Mater. Pal. Suisse, ser. 5), p. 211, 

 1887. — L. Mallada. Sinops, Espec. Pos. Espafia, vol. iii. Cret. 



infer. (Bolet. Com. Mapa geol. Espafia, 

 vol. xiv), p. 130. 



1 'Zeitschr. d. deutseh. geol. Gesellseh.,' vol. xlvii (1895), p. 473, pi. xvn, fig. . r >. 



