. Annals of the South African Museum = Annale van die Suid-Afrikaanse Museum . ngthen and are restricted to the ventral region, forming obtuse 116 ANNALS OF THE SOUTH AFRICAN MUSEUM chevrons at the siphonal line and weakly serrating the low keel. These dense prorsiradiateribs are about as wide as the interspaces, with 13 in a 15 mm distance at 50 mm are lacking but periodic low collars across the venter probably mark theirposition on the internal mould. Measurements Specimen D H W H/W U SAM-PCA1853 c, 72 30 (c. 42) ? ? 22 (c. 31) 44 17 (c. 39) 12 (c. 27) 11 (c. 25)

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. Annals of the South African Museum = Annale van die Suid-Afrikaanse Museum . ngthen and are restricted to the ventral region, forming obtuse 116 ANNALS OF THE SOUTH AFRICAN MUSEUM chevrons at the siphonal line and weakly serrating the low keel. These dense prorsiradiateribs are about as wide as the interspaces, with 13 in a 15 mm distance at 50 mm are lacking but periodic low collars across the venter probably mark theirposition on the internal mould. Measurements Specimen D H W H/W U SAM-PCA1853 c, 72 30 (c. 42) ? ? 22 (c. 31) 44 17 (c. 39) 12 (c. 27) 11 (c. 25) SAM-PCA1862 c. 54 24 (c. 44) 15 (c. 28) 18 (c. 33) ii 44 20 (45) 13 (c. 30) (c, 33) Discussion The present material differs from the fragmentary type material from the upper MiddleTuronian of northern Mexico in being more involute (umbilicus 25-33 vs. 37 per cent ofthe diameter) and somewhat more compressed (H/W = vs. ).However given the small amount of material currently available the differences, probably,are not taxonomically

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Keywords: ., bookcentury1800, bookdecade1890, booki, booksubjectnaturalhistory