On Cretaceous Cephalopoda from Ztiliilcnnl. 249 



Only in the Zululaud species, there generally is only a thick posterior 

 and a fine anterior branch, without the intermediaries found in both 

 the Dakota forms. The new form of Didymoceras, figured by Schliiter 

 on pi. xxxv, figs. 1-4, as jlet&roceras polyplocum?, showing bifurcation 

 only, is, perhaps, closer to the form here described in this respect, 

 but the tubercles are far too fine. The whorl-section is as compressed 

 as that of Schliiter 1 s loosely coiled form,* and less rounded than that 

 of D. '? newtoni, which has a larger umbilicus. That of the present 

 species is as small as the umbilicus of D. pauper, Whitfield sp., or that 

 of D. arcliiaciannm, d'Orbiguy sp., which latter also shows a similar 

 forward sweep of the costatiou on the under surface. 



Since the apex of the spire is not preserved, it is impossible to state 

 whether the early whorls were closely coiled, as seems probable from 

 the presence of a contact furrow on the upper surface of the highest 

 whorl, or whether the apex was an irregular spiral, as is the case in so 

 many forms of this group (Didymoceras). The coiling of the portion 

 that is preserved is the same as that of Tnrrlliti^ urnftis, Passy, also 

 recorded from Zululand by Crick. t " Turrilites" tridens, Schliitcr^ 

 also shows similar coiling, but the drawing appears deceptive, and the 

 writer is inclined to consider this species to belong to Hyphantoceras, 

 to judge by the uuder-surface of the whorls. 



If the form here described is a Nostoceras, it probably represents a 

 less specialised type than N. stantoni, Hyatt || ; for the single costae 

 with two lines of tubercles, so characteristic of Exiteloceras, are found 

 in the young of Nostoceras stantoni and of N. lieUcinum, Shumard sp.lj" 

 The latter form has a very short spire like the Zululand form, with a 

 deeply impressed suture, but the costatiou is quite different. 



Locality. TJmfolozi Valley, East of Railway. Coll. Mr. Illing- 

 worth. 



* This shows close resemblance to a beautiful specimen of Emperoceras 

 simplicostatum, Whitfield sp. (larger than the example figured by Whitfield, 

 ' Bull. Am. Mus. Nat. Hist.,' vol. xvi, 1902, pi. xxvii), in the B.M. (No. C10808), 

 and though the earlier whorls apparently are quite different from those of 

 Nostoceras and Didymoceras, the ornament of the last volution strikingly 

 recalls that of D ? newtoni, Whitfield sp., and of D ? cooperi (Gabb) Whiteaves 

 (B.M. from Vancouver). 



f Loc. cit. (1907), p. 176, pi. xi, figs. 3 and 4. 



J Loc. cit. (1872), pi. xxxv, fig. 9. 



The trituberculate (?) Turrilites peramplus Lasswitz (loc. cit., p. 14, pi. ii, 

 fig. 1) also resembles the present form somewhat in shape, but may be a true 

 Turrilites, though Lasswitz compares it with Schltiter's "Turrilites" tridens. 



|| Loc. cit. (1894), p. 570. 



If "Descr. of New Cret. Poss. from Texas," Proc. Boston Sou. Nat, Hist./ 

 vol. viii (1861), p. 190. 



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