Vol. 67.] KA1NOZOIC MOLLTJSCA FROM CYRENAICA. 631 



with no actual shell remaining ; and the surface has evidently been 

 subjected to some erosive action, as the costal system is very 

 depressed and in places obscure. The umbonal region is not 

 preserved. Both the valves are of nearly equal convexity, the 

 lower being well vaulted and of greater height than the upper, and 

 ornamented with numerous longitudinal more or less unequal costae 

 separated by narrow grooves, more prominent costae being placed 

 at equal distances over the surface, with two or three finer subsidiary 

 ones between. There are faint indications of distant concentric 

 lineations, as well as obscure evidence of asperities on the primary 

 longitudinal ribbing. This specimen in its oblong, oval contour and 

 general structure of the surface-sculpture resembles Fuchs's inter- 

 pretation of Brongniart's species S_p. cisaljrinns, which was obtained 

 from the Grumi Mountains of Castel-Gomberto, Northern Italy, and 

 is regarded as of Oligocene (Stampian) age. The specimen figured 

 by Fuchs is larger and in better condition than the original, which 

 was collected in the same area of Northern Italy, but in rocks said 

 to be ' Schioschichten ' and therefore of Aquitanian age. Both 

 Hoernes and Oppenheim have recognized the species in similar 

 rocks, while the latter author has also identified it as part of the 

 Priabonian fauna. The species, therefore, ranges from the Pria- 

 bonian to the Aquitanian. 



Dimensions. — Length =58 millimetres; height (approximate) = 

 80 mm. ; diameter = 35 mm. 



Occurrence. — The matrix is pale and of marly character, with 

 a reddish tinge in places. Microscopically it is made up of Litho- 

 thamnion, Operculina, etc., but without Nummulites. 



Locality. — Ain Sciahat (above camp). 



Pectex vezzanensis Oppenheim. (PI. XLV, figs. 3 & 4.) 



Pecten arcuatus E. Hoernes, Jahrb. K.K. Geol. Reichsanst. vol. xxviii (1878) 



pp. 18, 29, non Brocchi. 

 Janira arcuata Vinassa de Regny, Boll. Soc. Geol. Ital. vol. xv (1896) p. 204. 

 Pecten (Janira) vezzanensis Oppenheim, Zeitschr. Deutsch. Geol. Gesellsch. 



vol. lv (1903) pi. ix, figs. 6-7 a & p. 173. 



Remarks. — Dr. Oppenheim has described and figured a small 

 shell called Pecten vezzanensis, from the Aquitanian (Schioschichten) 

 rocks of Yezzan near Belluno, in Northern Italy, which had been 

 previously referred to in literature by Dr. Hcernes and Dr. P. Vinassa 

 de Regny as P. arcuatus, a species characteristic of the Priabonian 

 horizon. 



The specimen now assigned to this species consists of one lower 

 valve attached to some matrix, possessing twenty-one rather smooth- 

 topped ribs with minute transverse striations decorating the inter- 

 mediate furrows ; the ears are proportionately deep, the surface of 

 the byssal one being ornamented with three or four radial costse, 

 crossing a set of closely arranged, fine, vertical striations, while 

 the other is furnished with very obscure oblique lines. The um- 

 bonal area is narrow, less incurved than in other related forms, 

 and possessed of fairly long concave lateral margins which meet a 

 well-rounded ventral border. The valve is also moderately convex. 



