U'p2'>6r Palaeozoic and Mesozoic Fossils. 331 



Avith a tenacious matrix. Tlie suture lines are obscure. The 

 present specimen is smaller than that descrihed by Crick, having 

 a diameter of 45 mm., and with tlie width measurement of the 

 last whorl of 19 mm. 



This species was recorded by Crick from the same locality as 

 ours, and, as that author remarks,' it is evidently allied to 

 Ammonites braikenridgii, Sowerby, and which, according to 

 Munier Chalmas, is the type form of the genus Normannites. 

 ]\Ioore's specimen evidently came from the sauie district as the 

 above. 



Locality and Horizon. — Greenough River District, Western 

 Australia. Jurassic. [2068.]. 



Perisphi notes, Waagen. 



Perisphinctes championensis, Crick. 

 (Plate XXX., Fig. 2). 



Ammonites (Perisphinctes) championensis, Crick, 1894. Geol. 

 Mag., Dec. iv., vol. i., p. 436, pi. xiii., figs. '2a-c. 



The specimen figured liy Crick is precisely similar to the pre- 

 sent example iu its essential characters, so far as the preservation 

 of the latter enahles one to see. The inner whorls are obscured 

 by a tenacious matrix. 



The dimensions of the present specimen are somewhat greater 

 than those given by Crick, and are as follows : — - 



Diameter of shell ... ... 135 mm. 



Width of umbilicus, about ... 45 mm. 



Height of outer whorl ... ... 60 mm. 



Thickness of outer whorl ... 46 mm. 



An extremely interesting feature is exhibited in this specimen 

 in the occurrence of the aptychus, lying towards the extremity of 

 the last whorl of the .shell and close against the ventral surface 

 of the living chamber. It was revealed by the fracture and 

 removal of one side of the outer whorl of the ammonite shell. 

 One valve of the aptychus is nearly complete, with a portion of 

 the adjoining plate; the apparent line of junction of the two 

 halves in this instance is, however, misleading, as they are the 



1 Loc. cit., p. 392. 



10a 



