68 Annals of the South African Museum. 



The delicate notched structure is also well shown in specimens from 

 the above-mentioned locality near Uitenhage. 



Tate brought this shell into relationship with Pecten lens Sowerby, 

 a Jurassic form ; and although it shares with this and with the 

 Portlandian P. morini de Loriol * some of the principal features which 

 characterise these familiar Jurassic types, yet it may equally well be 

 brought into comparison with Cretaceous forms. The Jurassic 

 shells mentioned, besides differing in the outline, have simply striae 

 with a punctate structure, but no encroachment of this sculpture into 

 the interspaces between the linear striae. Pecten suprajurensis 

 Buvignier,f an Upper Jurassic form, approaches much more closely 

 to P. projectus in general character and outline, possessing a similar 

 bulging frontal profile, but is likewise merely ornamented by delicately 

 punctate linear striae with smooth interspaces, attaining, moreover, 

 much larger dimensions. Pecten buchi Roem.,J also Upper Jurassic, 

 is well distinguished by its almost equilateral outline and by the minute 

 transverse striations which cross the interspaces between the radial 

 linear striae. 



Pecten striato-punctatus Eoemer, from the Neocomian and Aptian 

 of Europe, is more equilateral in outline and is more delicately 

 ornamented; the punctate structure is much more minute and 

 confined wholly to the striae, leaving the very narrow intervening 

 spaces smooth. 1 1 



Pecten curvatus Geinitz, II though having greater relative height 

 than P. projectus, sometimes seems to approach the somewhat in- 

 equilateral form of this, though in figures of other shells which have 

 been united with P. curvatus** the valves are almost equilateral. 

 Although Geinitz figured the magnified ornamentation of the valve- 

 surface so as to produce an aspect of sculpture widely different from 

 that given for instance by Eeuss, yet it appears from the descriptions 

 that punctate linear striae with smooth interspaces characterise these 

 forms. 



Nilsson's P. virgatus, of Upper Chalk age from Sweden, ft is 



* de Loriol and Pellat (1), p. 107, pi. x., fig. 6. 



t Buvignier (1), p. 24, pi. xix., figs. 21-23. 



} F. A. Koemer (1), pi. xiii., fig. 8 (1836), and Nachtrag, p. 27 ; de Loriol, Koyer 

 and Tombeck (1), p. 389, pi. xxii., figs. 12, 13. 



F. A. Koemer (1), Nachtrag, p. 27; d'Orbigny (3J, p. 592, pi. 432, figs. 4-7 

 (1847); Woods (3), vol. i., p. 157, pi. xxix., figs. 4-6 (1902). 



|| See also figures given by de Loriol under the name P. arzierensis ; Loriol (3), 

 pi. iv., figs. 3-5. 1[ Geinitz (1), p. 16, Taf. iii., fig. 13. 



** Geinitz (2), Theil i., p. 193, Taf. 43, fig. 15 (1872) ; Theil ii., Taf. 10, fig. 1, 

 (1872) ; Beuss (1), part ii., p. 28, Taf. 39, fig. 6 (as P. divaricatus). 



ft Nilsson (1), p. 22, Tab. ix., fig. 15. 



