. Annals of the South African Museum = Annale van die Suid-Afrikaanse Museum. Natural history. 300 Annals of the South African Museum. they are low. Furthermore, although, some forms have upstanding and others inclined iliac blades, this hardly affects the total pelvic height. —The ilia vary greatly in size and shape. Some of these varieties were used by Watson (31) in defining the Pareiasaurian genera known to him. With reference to the vertical plane passing through the centre of the acetabulum, the ilium is inclined at a smaller or greater angle. In the former case we shall speak of
. Annals of the South African Museum = Annale van die Suid-Afrikaanse Museum. Natural history. 300 Annals of the South African Museum. they are low. Furthermore, although, some forms have upstanding and others inclined iliac blades, this hardly affects the total pelvic height. —The ilia vary greatly in size and shape. Some of these varieties were used by Watson (31) in defining the Pareiasaurian genera known to him. With reference to the vertical plane passing through the centre of the acetabulum, the ilium is inclined at a smaller or greater angle. In the former case we shall speak of an upstanding or vertical ilium, and in the latter of a forwardly directed ilium. The dorso-ventral measurement of the iliac blade may be small or great, and we thus distinguish low or high blades ; similarly, some blades are long and others short. In those forms with forwardly directed blades it is found that the iliac shaft is either long or short, whereas in those with upstanding ilia the shaft is invariably long. This shaft may be more or less constricted—a character concomitant with either upstanding or inclined ilia. Posteriorly the ilia may have weakly or strongly developed processes—a feature not connected with the forward inclination or upstanding nature of the ilium. The antero- ventral border of the iliac blade varies greatly; so does the external surface. The external surface may be flat or concave in antero- posterior direction, and the antero-ventral edge may be turned out- wards to some degree, or it may not be everted at all. This eversion of the edge must not be confused with another variation of the ilium ; in postero-anterior direction the whole blade of the ilium may be diverging with reference to the medial vertical plane—a feature which reaches its height in Mammals. This divergence seems to be restricted to the forms with forwardly directed ilia. Many of these forms have broad pelves, and the width between the two ilia therefore becomes very great
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectnaturalhistory, booky
