Vol. 67.] KAINOZOIC MOLLUSCA FROM CYRENAICA. 635 



Oopecten rotundatus Sacco, ' Moll. Terr. Terz. Piemonte ' 1897, pt. 24, pi. xv, 



figs. 14-15 & p. 54. 

 Pecten (Oopecten) rotundatus R. B. Newton, ' Marine Tertiary [Miocene] 



Mollusca from Lake Urmi, Persia ' Linn. Soc. Journ. (Zool.) 1900, vol. xxvii, 



pi. xxix, fig. 1 & p. 443. 



He marks. — The pectinoid shells referred to this species have 

 well accentuated costse varying in number like the original from 

 about fourteen to sixteen, which are at first well rounded but later 

 become more or less depressed at the summits ; both the costse 

 and furrows widen out ventrally and are of equal width. The 

 surface of the valve is covered with closely-set concentric striations, 

 which are more obscure over the umbonal region. The best- 

 preserved specimen in the collection shows an almost similar length 

 and height of about 70 millimetres, but the margins are by no 

 means perfect, otherwise it is possible that the length may have 

 exceeded the height, as in normal forms of the species ; the auricles 

 are only partly seen. The species was originally described from 

 Vence, between Grasse and Nice in France, under the following 

 diagnosis: — testa suborbiculari utrinque convexa; radiis 

 14 ad 16 distinctis, convexis, versus limbum planu- 

 latis, two figures in Knorr's old folio work 1 being mentioned as 

 examples ; but it is evident, as pointed out by Deshayes, that they 

 belonged to entirely different forms of pectiniform shells ; more- 

 over, one (op. cit. fig. 5) was from Malta, the other (fig. 6) was 

 from Algiers. The figure of the Maltese specimen comes probably 

 nearest to a proper conception of the present species although of 

 less size, and as Deshayes explained, it should not be considered the 

 same shell because only seven costal ribs are present. Bearing in 

 mind also that this same figure represents an imperfectly preserved 

 specimen, it is advisable to dismiss it from synonymy, a plan fol- 

 lowed by most subsequent authors. According to Prof. Sacco the 

 species ranges from the top of the Aquitanian to the Helvetian in 

 Italy. Fuchs regarded the Vence forms as of ' Horner Schichten r 

 age, and consequently Aquitanian or lowest Miocene ; Fontannes's 

 Eh one Valley specimens were considered as Lower Helvetian ; 

 while the Persian specimens from the Siokuh Mountains and from 

 Lake Urmi have been bracketted with the Helvetian or Burdi- 

 galian stages of the Miocene. 



Occurrence. — The matrix varies from a cream-coloured or 

 greyish limestone to a yellowish, arenaceous marly-looking rock 

 with minute blackish grains ; and all have the usual external 

 ferruginous tinting. Operculina and Nullipore structures (in valves 

 from Ain Sciahat) are frequent, besides Lepidocyclina elepliantina, 

 identified by Mr. Chapman (see his report on the Foraminifera of 

 the present collection, p. 660), who states that it indicates either 

 a Stampian or an Aquitanian age. The presence of the mollusc, 

 however, in this case would favour the latter horizon. 



Localities. — West of Labruk ; Birlibah ; Wadi Umzigga (second 

 camp) ; and Ain Sciahat. 



1 ' Kecueil de Monumens des Catastrophes . . . Petrifications ' vol. ii (1768) 

 sect. 1. p. 77 & pi. Bl c, figs. 5-6. 



Q.J.G.S. No. 268. 2x 



