Vol. 67.] KAINOZOIC MOLLTTSCA FROM CZRENAICA. 623 



Linnaeua, both found living in the Mediterranean. Deshayes, how- 

 ever, has pointed out (on the authority of Hanley, ' Ipsa Linnaei 

 Conchylia' 1855, pp. 99 & 100) that in Glycymeris glycymeris 

 the concentric striations are more obvious and the valves generally 

 more depressed. In addition, it would appear that the contour of 

 Gl. pilosa is more or less elongate, whereas in the other species 

 it is usually much rounder. 



Dimensions (left valve). — Length = 48 millimetres; height 

 = 52 mm. ; diameter = 20 mm. 



Prof. Sacco has recorded this shell from the Tertiary deposits 

 of Italy, regarding its range as extending from Helvetian times. 

 It occurs in the Pliocene (Coralline Crag) of England, where 

 Searles Wood has recognized it under Pectuacidus glycymeris, 

 showing varietal characters of P. inflatus and P. insubricus of 

 Brocchi. 



Occurrence. — The matrix is a cream-coloured limestone, 

 coated with a thick brick-red rock which is also of calcareous 

 composition. 



Locality. — West of Ptolemeta. 



Cerastodeema edule (Linnaeus). (PI. XLIII, figs. 9 & 10.) 

 [Additional synonymy to that on p. 621.] 



Cardium crassum Defiance, Diet. Sci. Nat. [Paris] 1817, vol. v, Suppl. p. 106, 



non Gmelin ; Philippi, ' Enumeratio Molluscorum Siciliae ' 1836, pi. iv, tig. 17 



& p. 53. 

 Cardium rasticum Eichwald, ' Fauna Caspio-Caucasia ' 1841, pi. xxxviii, 



figs. 26-27 & p. 215, non Linnaeus. 

 Cardium edule [pars], iimbonatum, etc., Searles V. Wood, Monogr. Pal. Soc. 



(British Crag Mollusca) 1853, pi. xiv, figs. 2a-2g & p. 155. 



"Remarks. — This species exhibits many variations, but, speaking 

 generally, the examples of the present collection appear to favour a 

 form figured by Searles Wood from the English Crag, called C. edule 

 var. umbonatum, which has produced and inflated umbones as 

 well as thick and well-defined costse ; it is the same as Eichwald's 

 C. rusticum, which lives in the brackish waters of the Aralo-Caspian 

 region of Europe, being also found fossil in the shore-deposits of 

 that district. The specimens likewise resemble a fossil from Sicily 

 described and figured by Philippi as Cardium crassum, which, so 

 far as the figure is concerned, shares all the characters of the 

 forms from Cyrenaica. The costae are subangulate and ornamented 

 at first with extremely fine concentric striations which have the 

 appearance of delicate annulations, these afterwards giving place 

 to a coarser condition of annulated structure, the segments of 

 which become so thick that they resemble nodosities. All the 

 valves are of thick and robust character. 



Dimensions (large example with united valves). — Length = 

 40 millimetres; height=30 mm.; diarneter=28 mm. 



Specimens of this shell are numerous. The species is known 

 from other areas of Northern Africa, and likewise from most 

 countries skirting the Mediterranean Sea, in rocks of similar age ; 

 Prof. Sacco and Searles Wood, however, have recognized it in the 

 Pliocene of Italy and England, and it is besides known as a living 



