from Western Australia. 437 



men, probably referable to this species, which exhibits a portion of 

 the suture-line that supplements in a certain degree the suture-line 

 of the example selected as the type. The collection also contains, 

 from "Cape Eiche, about 50 miles E. of Albany," a large specimen 

 160 mm. in diameter, which is probably a more mature example of 

 this species. It consists of the outer whorl only. Although its 

 suture-line cannot be made out, its general form resembles that of 

 the present species so closely that it is referred to this species. 



The present species appears to be represented in the British 

 Museum Collection by a crushed and distorted portion of the outer 

 whorl of an example from "the Greenough, Champion Bay," about 

 110 mm. in diameter (No. C. 4708). It bears fragments of the test. 



Probably to this species may also be referred an example in the 

 collection of Western Australian fossils in the Bath Museum. It 

 is labelled "Ammonites macrocepJialus" ; but is not the specimen 

 figured by Moore. It has the following dimensions : Diameter of 

 shell, 109 mm. ; width of unibilicus, 37 mm. ; height of outer whorl 

 above preceding whorl, 27 mm. ; thickness of outer whorl, 40 mm. ; 

 width (as seen within the umbilicus) of the penultimate whorl at the 

 greatest diameter of the shell, 12 mm. The body-chamber com- 

 mences where the shell has a diameter of 88 mm., and therefore 

 occupies nearly a whorl. 



Affinities and differences. — This species greatly resembles Ammonites 

 Cautleyi,^ Oppel, from the Jurassic rocks of Laptel, in Gnari-Khorsum, 

 Thibet; but Oppel's species possesses constrictions and is a more 

 compressed shell. Unfortunately the suture-line is not available in 

 Oppel's species for comparison. Compared with Ammonites albineus," 

 Oppel, from the Oxfordian of Wiirtemberg, the Australian species 

 is more robust and has a different suture-line. In Oppel's species, 

 moreover, the ribs which cross the periphery disappear at a diameter 

 of 75 mm., but they are quite distinct in the Australian specimen at 

 a diameter of 110 mm. The present species differs from Ammonites 

 pohjmoi-pJius,^ d'Orbigny, from the Inferior Oolite, in having ^ more 

 inflated whorls, larger and fewer tubercles around the umbilicus, 

 and ribs which are uninterrupted on the peripheral area. Although 

 somewhat resembling Perisphinctes obtusicosta * and Ferisph. para- 

 morphiis,^ Waagen, from the Callovian of Cutch, the Australian 

 species has much finer ornaments and a very different suture-line. 



The general arrangement of the suture-line is not unlike that of 

 Olcostephanus Brancoi,^ Neumayr and Uhlig, but the lattter is a more 

 inflated and more coarsely ornamented species. The ornamentation 

 of the present form agrees somewhat closely with that of Olco- 

 stephanus Keyserlingi,'' Neumayr and Uhlig, but the suture-line of 



1 Pal. Mittheil. p. 279, pL Ixxviii. figs, la, h ; 2a, b. 



2 Ibid. p. 161, pi. 1. figs. 3a, b. 



3 Pal. Pran(j. Terr. Jur. vol. i. 1842, p. 379, pi. cxxiv. 



* Pal. Indica, Jurassic Fauna of Cutch., vol.'i. (Cephalopoda), p. 146, pi. xxxvm. 

 figs, la, b; 2 ; 3a, b. 



5 Ibid. p. 162, pi. xlvi. figs, la, b; 1a,b\ pi. xlvii. fig. 3. 

 ^ Palseontographica, vol. xxvii. p. 156, pi. xxvi. fig. 1. 

 ' Ibid. p. 155, pi. xxvii. figs. 1-3. 



