from Western Australia. 435 



specimen 64 mm. in diameter. It is a natural cast, and bears only 

 fragments of the test ; its outer whorl appears to have been occupied 

 by the body-chamber, traces of the septa being seen at the commence- 

 ment of this whorl. 



Having examined the specimen figured by Moore as Ammonites 

 Brocchii,^ I believe it is to be referred to the present species. Its 

 dimensions are as follows : — 



Diameter of shell 92 mm. 



Width of umbilicus 33 ,, 



Height of outer whorl about 33 ,. 



The thickness of the outer whorl at a diameter of 72 mm. is 

 36 mm. ; beyond this point the specimen is much crushed. The 

 shell is somewhat distorted, so that the width of the umbilicus is 

 probably exaggerated. Its suture-line cannot be made out, but 

 around the umbilicus can be seen the compressed, forwardly-inclined, 

 short primary ribs, each giving rise to three or four prominent ribs, 

 which pass without intei'ruption over the peripheral area. 



To the present species may also probably be referred a specimen 

 (No. C. 4709) in the British Museum (Nat. Hist.), from "the 

 G-reenough, Champion Bay, Australia." It is part of a specimen 

 127 mm. in diameter ; the inner whorls up to a diameter of 25 mm. 

 are fairly well preserved, the innermost being perfectly smooth ; 

 about half of the outer whorl is present and in fair condition, and 

 shows the compressed umbilical tubercles or short prominent primary 

 ribs, each branching into three less prominent, but well-marked, ribs, 

 which cross the periphery without interruption. On the anterior 

 half of the outer whorl the primary ribs are more forwardly-inclined 

 than on the posterior half. A projection on the lateral area at the 

 anterior extremity of the specimen may be a portion of the pro- 

 minent mouth-border. The sculpture of the posterior part of the 

 outer whorl greatly resembles that of the large specimen from 

 Cape Riche, which I have referred to Ammonites (Perispliinctes) 

 Championensis (see p. 436), but the latter appears to have been a 

 more inflated shell. 



Affinities and differences. — J. Sowerby's type-specimens of Am- 

 monites Brocchii ^ are much more inflated than the present species, 

 whilst the type-specimen of Ammonites Brodicei " of the same author 

 has more distinct and somewhat larger primary ribs and very pro- 

 minent tubercles at the points of subdivision of the primary ribs. 

 Ammonites contractus ^ of J. de C. Sowerby is a much more inflated 

 shell with a smaller umbilicus. D'Orbigny's figure of Ammonites 

 linguifenis^ represfents a more inflated shell, with more numerous 

 ribs and more prominent lateral tubercles; and Ammonites dimorpJius ^ 

 of the same author has fewer whorls, a differently-formed umbilicus, 

 and its whorls bear constrictions at nearly regular intervals. 



1 Quart. Journ. Geol. Soc. vol. xxvi. (1870), pi. xv. f. 4. 

 * Min. Con. vol. ii. p. 233, pi. 202, both figs. [Brit. Mus. Xo. 43906]. 

 3 Min. Con. vol. iv. p. 71, pi. 351 [Brit. Mus. No. 43905], 

 " * Min. Con. vol. v. p. 162, pi. 500, f. 2. 

 6 Pal. Fran^. Terr. Jur. vol. i. pi. 136. 

 ^ Pal. Fran9. Terr. Jur. vol. i. pi. 141. 



