Annals of the South African MuseumAnnale van die Suid-Afrikaanse Museum . k costae, to cross the area obliquely and pass weakly on to theouter part of the escutcheon. Later flank costae are discrepant, with a coarse,robust, distant, strongly oblique anterior set of about 10-13 ribs that pinch andswell irregularly but do not form true nodes. These costae curve stronglyupwards posteriorly to become subvertical, whereas anteriorly they may zigzagor break up into pustules; in large specimens they become effaced anteroven-trally. Then follow about seven similar ribs that are subvertical and only we
Annals of the South African MuseumAnnale van die Suid-Afrikaanse Museum . k costae, to cross the area obliquely and pass weakly on to theouter part of the escutcheon. Later flank costae are discrepant, with a coarse,robust, distant, strongly oblique anterior set of about 10-13 ribs that pinch andswell irregularly but do not form true nodes. These costae curve stronglyupwards posteriorly to become subvertical, whereas anteriorly they may zigzagor break up into pustules; in large specimens they become effaced anteroven-trally. Then follow about seven similar ribs that are subvertical and only weaklycurved. The posterior set of c. 18 costae are narrow, crowded, somewhat undu-latory, broader than the interspaces, almost straight, and inclined postero-ventrally. Ribbing is effaced posterodorsally, just before reaching the area, toleave a small portion of the flank smooth. Occurrence Megatrigonia conocardiiformis (Krauss) is reported from the Upper Titho-nian of northern Mozambique, the Upper Valanginian of the Algoa Basin, 30 ANNALS OF THE SOUTH AFRICAN MUSEUM v. ^^jgf ,r
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Keywords: ., bookauthorsouthafr, bookcentury1800, bookdecade1890, bookyear1898
