254 Annul* of the South African Museum. 



as " Heteroceras ? sp. ind.," agree with the specimens here described in 

 whorl- shape and coiling, but all have oblique costation. 



A fragment of a " Heteroceras sp.," from the " Iron Mines of Hok- 

 kaido, Japan" (B.M., No. C10410B) resembles the South African 

 form in coiling and whorl-section, and being a cast, in the faint 

 ribbing, but it is considerably larger. Its suture-line is " lytoceratid,' 1 

 like that of Pravitoceras tnjuinitlale, Yabe,* which it closely resembles, 

 and it is associated with fragments comparable with the inner, closely 

 coiled whorls of Pravitoceras^ and with the terminal portion of such 

 a species of Bostrychoceras or Didymoceras, as, e.i/., the variety of 

 " Heteroceras polyplocus" figured by Schliiter on pi. xxxiv, figs. 2 and 3, 

 or D. ? cooperi, Grabb, in Whiteaves.J The age of Pravitoceras 

 unfortunately is not known, but it is to be noted that the suture-line 

 of the South African form, figured by Woods, and that of the 

 Turouiau Hyphantoceras, are very similar to that of Pravitoceras, and 

 the writer is of opinion that the resemblance of all these to the suture- 

 line of Lytoceratidae is a case of convergence, correlated with the 

 rounded whorl-shape. Nip2 } onites^ also represents a development 

 related to the loosely-coiled Bostnjclioceras here discussed, but the 

 reference of the South African form to this genus cannot, of course, be 

 considered definite so long as only fragmentary specimens are avail- 

 able. The young of Emperoceras\\ show hamitid, helicoid coiling, and 

 the twisted form figured by Woods^f as Haniites (Anisoceras), sp., 

 seems to form a transition to such species as " Ancyloceras" retrorsum, 

 Schliiter, and to the group of " Anisoceras" referred to in the description 

 of Diplomoceras ? indicnni, which groups stand in the same relation- 

 ship to Bostrychoceras as (ptychoceratid, hamitid or ancyloceratid) 

 Oxybeloceras** does to Exiteloceras. The similarity, however, of the 



* " Note on Three Upper Cretaceous Ammonites etc.," ' Jl. Geol. Soc. 

 Tokyo/ vol. ix (1902), No. 100, p. 3, pi. i, fig's. 2-4. 



t Ibid., fig. 3. 



J Loc. cit., p. 336, pi. xliii, fig. 1. 



Yabe, loc. cit. (1904), p. 20, pi. iv, figs. 4-7, pi. vi, fig. 6. 



|| Hyatt, loc. cit. (1894), p. 575, pi. xiv, figs. 15-17. 



If Loc. cit., p. 340, pi. xliv, fig. 3. 



** Unless new genera are introduced again for the different forms of coiling, 

 such species as "Hamites" wernickei, Wollemann ("Fauna d. Liineburger 

 Kreide," ' Abh. K. Preuss, L A.,' N.F., Heft. 37 (1902), p. 95, pi. iv, fig. 4, and pi. v, 

 figs. 1 and 2 crushed?), or "Ancyloccras" lipunctatum, Schliiter (loc. cit., p. 98, 

 pi. xxix, figs. 1-3), will have to be included in Oxybeloceras, whereas " Crioceras " 

 plicatilis, Kner, non Sowerby (Lemberg, ' Natunv. Abh.,' iii, 1850, pt. 2, p. 9, 

 pi. ii, fig. 3) = Helicoceras schloenbachi, Favre ('Moll. Craie, Lemberg,' 1869, 

 p. 30, pi. vii, figs. 5 a-c), and Helicoceras hibernicum, Tate, possibly belong to 

 Exiteloceras. The presence of at least one other unnamed group is indicated by 



