132 



Radstockiceras buvignieri (d'Orbigny, 1844) PI. 5, fig. 1 



1844 Ammonites buvignieri d'Orbigny: 261, pi. 74, figs 1-3. 



1855 Ammonites complanosus Simpson: 79, 80. 



1855 Ammonites retentus Simpson: 84. 



1920 Retenticeras retentum (Simpson); Buckman: pi. 166 



(holotype, GSM 26401). 

 1962 Metoxynoticeras complanosum (Simpson); Howarth: 105, 



pi. 15, fig. 4 (holotype, WM 239, now lost). 

 1992 Radstockiceras complanosum (Simpson); Schlegelmilch: 



60. pi. 54, fig. 2 (WM 239). 

 1994 Radstockiceras buvignieri (d'Orbigny); Fischer: 67, pi. 2 1 , 



fig. 3 (holotype, from Breux, Meuse, France). 



Remarks. Occurs in beds 494, Macdonnelli Subzone, 505.2, 

 Taylori Subzone, and 544.7, Brevispina Subzone; 7 specimens. 



Measurements (in mm) 





D 



Wh 



Wb 



U 



CA 3744 



167.0 



94.5(0.57) 



42.0 (0.25) 



7.0 (0.04) 



CA 3744 



138.5 



79.0(0.57) 



33.5 (0.24) 



6.3 (0.05) 



REMARKS. The four examples obtained from bed 494 are all large 

 specimens of 145-250 mm diameter preserved in grey limestone. 

 The best one (PI. 5, fig. 1 ) is wholly septate up to its maximum size 

 of 168 mm diameter. The single specimen from bed 505.2 is a well- 

 preserved fragment of a part of a whorl, with whorl height 72 mm and 

 whorl breadth 27 mm (if the whorl height is 0.57 of the diameter, then 

 the whorl breadth is 0.21 of the diameter). One of the two pyritized 

 specimens found in bed 544.7 is 25 mm diameter and is similar to the 

 holotype of 'Retenticeras' retentum figured by Buckman (1920: pi. 

 166). With their very small umbilici (4-5% of the diameter) and 

 compressed whorl sections (whorl breadth 21-25% of the diameter), 

 all appear to be genuine examples of Radstockiceras buvignieri, of 

 which the holotype (Fischer, 1994: 67, pi. 21, fig. 3-178 mm 

 diameter, 99 (0.56), 37 (0.2 1 ), 6 (0.03 )) has closely similar characters. 

 The holotype of Simpson's species complanosum, and the almost 

 identical specimen BM 37960 (from Robin Hood's Bay), undoubt- 

 edly belong to the same species, but it is difficult to identify their 

 horizons - they could have come from any of the beds 494, 505 and 

 544. 



M.K. HOWARTH 



15 specimens; 2 specimens of Cymbites sp. indet. occur slightly 

 higher in beds 464.32 and 464.33. 



Remarks. The main species present in Robin Hood's Bay is C. 

 laevigatus, but a more compressed species with obsolete ribbing, eg. C. 

 fastigatus Schindewolf (1961: 211, pi. 30, figs 8-10), may also be 

 present amongst the small specimens determined as Cymbites sp. 

 indet. in the Denotatus and Simpsoni Subzones. 



Superfamily EODEROCERATACEAE Spath, 1929 



Family EODEROCERATIDAE Spath, 1929 



Genus MICRODEROCERAS Hyatt, 1871 



Microderoceras scoresbyi (Simpson, 1843) 



1843 Ammonites scoresbyi Simpson: 12. 



1911 Xipheroceras scoresbyi (Simpson): Buckman: pis 39A. B 

 (holotype, WM 1 73). C (topotype, GSM 23616), both prob- 

 ably from bed 441 .2. 



RANGE. One specimen found in bed 441.2, Birchi Subzone. 



Remarks. This single specimen differs from M. birchi in having 

 higher and thicker whorls that are slightly less evolute. 



Microderoceras birchi (J. Sowerby, 1820) 



PI. 5, fig. 7 



1820 Ammonites birchi J. Sowerby: 121, pi. 267. 



1 96 1 Microderoceras birchi (J. Sowerby); Dean et al. : pi. 66, fig. 



3 (BM 67973, from the Dorset coast). 

 1973 Microderoceras birchi (J. Sowerby); Donovan & Forsey: 



10. pi. 1, fig. 1 (lectotype, BM 43923, from the Dorset 



coast). 



Range. Found only in bed 433.3, Birchi Subzone; 5 specimens. 



Remarks. The five large specimens in bed 433.3 have typical very 

 evolute whorls, with bituberculate ribs up to the end of the largest 

 specimen at 235 mm diameter, and considerable variation in whorl 

 thickness. The specimen figured in PI. 5. fig. 7 appears to have a 

 complete body-chamber nearly 1 Vi whorls long, ending in an ( ?adult ) 

 aperture at 210 mm diameter. 



Radstockiceras sphenonotum (Monke, 1888) PI. 5, fig. 4 



1888 Ammonites sphenonotus Monke: 228. pi. 2/3, fig. 14 



(holotype, from Germany). 

 1914 Oxynoticeras sphenonotum (Monke); Pia: 65, pi. 7. fig. 12. 



Range. Beds 542.1-544.4, Polymorphus Subzone; 8 specimens. 



Remarks. The best preserved specimen occurs in bed 544.4 (PI. 5, 

 fig. 4). 



Family CYMBITIDAE Buckman, 1919 

 Genus CYMBITES Neumayr, 1979 



Cymbites laevigatus (J. de C. Sowerby, 1827) PI. 5, fig. 6 



1827 Ammonites laevigatus J. de C. Sowerby: 135, pi. 570, fig. 3. 

 1957 Cymbites laevigatus (J. de C. Sowerby); Donovan: 413, figs 



1-8 (topotypes (the holotype is lost), from Brooki to Stellare 



Subzones, Dorset coast). 



Range. Beds 446.5^464.1, top Obtusum to Simpsoni Subzones; 



Genus XIPHEROCERAS Buckman, 1911 



Xipheroceras dudressieri (d'Orbigny, 1845) PI. 5, fig. 2 



1845 Ammonites dudressieri d'Orbigny: 325. pi. 103, figs 1, 2. 

 1926b Xipheroceras dudressieri (d'Orbigny); Spath: 172, pi. 9. 



fig. 6 (BM C. 2235a, a typical example from the Obtusum 



Subzone, Dorset). 

 1994 Xipheroceras dudressieri (d'Orbigny); Fischer: 91, pi. 19, 



fig. 3 (from Mulhausen. France). 



Range. One specimen in bed 446.33, Obtusum Subzone. 



Xipheroceras ziphus (Zieten, 1830) 

 1830 



PI. 5 fig. 5 



Ammonites ziphus Zieten: 6. pi. 5, fig. 2 (holotype, BM 



62590. from Heiningen, Wurttemberg, Germany). 

 1926 Xipheroceras ziphus (Zieten); Buckman: pi. 732 (GSM 



47832, coarsely ribbed inner whorls, from the Obtusum 



Subzone, Dorset). 

 1928 Xipheroceras revertens Buckman: pis 772 A, B (a typical 



large example of X. ziphus from the Obtusum Subzone. 



Dorset). 



