DICYSTODONTID^:. 39 



R. 1294. The imperfect middle region of an immature cranium, 

 showing impressions of the sclerotic plates in the orbit ; 

 from near Colesberg. Noticed by Huxley in the ' Quart. 

 Journ. Geol. Soc' vol. xv. p. 657. There appear to have 

 been four or five bones in the sclerotic ring ; and there 

 is an azygous " Wormian bone " in front of the parietal 

 foramen, as in No. 36253. 



Presented by Prof. T. H. Huxley, 1888. 



33224. The imperfect and somewhat distorted cranium of a half- 

 (Fiy-) grown individual; from the Beaufort beds of the Karoo 

 system of the Rhenosterberg branch of the Sneewberg 

 range. The type of P. vertlcalis ; figured by Owen in tho 

 ' Quart. Journ. Geol. Soc' vol. xvi. pi. i. fig. 2, and also 

 in his ' Catalogue of the Fossil Heptilia of S. Africa,' 

 pi. xlix. figs. 1, 2. This specimen agrees very closely in 

 contour with the type, but the convexity of the frontal 

 region is less marked, which may be due partly to crushing 

 and partly to immaturity. 



Presented by Sir George Grey, K.O.B., 1858. 



33253. The imperfect skull of a slightly larger individual, attached 

 (Fiy.) to a mass of matrix containing vertebne and other bones ; 

 from the Rhenosterberg. The type of P. boopis ; figured 

 by Owen in his ' Catalogue,' pi. xlviii. fig. 1, and pi. xlix. 

 fig. 3. The orbit is not perceptibly larger than in the 

 preceding specimen ; the alleged larger size of the nares and 

 their approximation to the orbit is a feature of the right 

 side of the specimen due to imperfection, the left nares 

 being precisely the same as in the preceding specimen. 

 The contour of the frontal region is similar to that of the 

 type. This specimen is important, as showing the com- 

 position of the temporal arcade ; the squamosal (27 of 

 Owen's figure) is seen overlying the upper part of tho 

 quadrate ( = tympanic, 28, of Owen), and is itself con- 

 nected both with the postfrontal and the maxilla, without 

 any sign of a distinct jugal. Since the quadrate has no 

 connecting chain with the maxilla, the one temporal 

 arcade may be termed squamoso-maxillary, and thus cor- 

 responds with the Mammalian zygomatic arcade \ In 



1 This interpretation of the relations of the bone of the temporal arcade 

 agrees with that given by Seeley in the ' Phil. Trans.' for 1889, p. 244, fig. 2. 



