LOWER LIAS OF ROBIN HOOD'S BAY 



125 



cal width is 38^40% of the diameter; the whorls are quickly expand- 

 ing and massive, the whorl breadth is large, and the venter is 

 tricarinate-bisulcate, but loses the sulci at the largest sizes; inner 

 whorls have radial ribs and small ventro-lateral tubercles, but all 

 ornament fades by 230 mm diameter. 



Description. Before removal from the rock, Bairstow measured 

 the holotype as having a crushed outer whorl ending at 480 mm ('19 

 inches' ) diameter. At that size it was probably complete, but the part he 

 collected in 1933 is solid and uncrushed up to the end of the 

 phragmocone at 330 mm diameter, followed by a short portion at the 

 begining of the crushed body-chamber ending at about 350 mm 

 diameter. Slightly more than one whorl up to the end of the phragmocone 

 is preserved, to which is attached a small portion of the upper part of the 

 side of the next inner whorl. These whorls are massive, rapidly expand- 

 ing, moderately evolute, and have a whorl section in which the whorl 

 sides converge slightly towards the tricarinate-bisulcate venter, which 

 has a strong central keel. Moderately strong radial ribs fade and 

 disappear three-quarters of a whorl before the end of the phragmocone, 

 and the remaining whorls are smooth. 



The larger paratype (CA 3218) consists of inner whorls up to 40 

 mm diameter, but only a quarter of a whorl up to 25 mm is well 

 preserved. This has quadrate, moderately evolute whorls with a 

 tricarinate-bisulcate venter, and strong straight radial ribs up to small 

 ventro-lateral tubercles; the ribs then bend strongly forwards on the 

 side of the venter and join the lateral keels. 



The smaller paratype (CA 3219) consists of small inner whorls up 

 to only 12.5 mm diameter. Its whorl shape, ribs and tubercles are 

 similar to those of the larger paratype. 



Measurements (in mm) 





D 



Wh 



Wb 



U 



CA3217 



342 



116(0.34) 



90 (0.26) 



136(0.40) 



CA3217 



265 



92 (0.35) 



67 (0.25) 



101(0.38) 



Remarks. This is the oldest Eparietites and is more evolute than 

 any of the succeeding species. The large holotype has massive 

 whorls, with a quadrate whorl section in which the whorl sides 

 converge only slightly towards the venter, a large whorl breadth, and 

 a tricarinate-bisulcate venter; the sulci bordering the central keel on 

 the venter slowly disappear at the largest sizes. E. impendens occurs 

 higher up at Robin Hood's Bay and has much more compressed and 

 involute whorls, the umbilical width being 22-24% of the diameter 

 compared with 38^4-0% in E. bairstowi. 



Many Eparietites occur in the Denotatus Subzone in the top 0.5 m 

 of the Frodingham Ironstone at Scunthorpe, Lincolnshire. Speci- 

 mens attain very large sizes, some in the NHM collections being up 

 to 600 mm diameter. Most of the smaller specimens are E. impendens, 

 but the larger specimens belong mainly to the more evolute species 

 Eparietites undaries (Quenstedt), in which the umbilical width is 

 27-34% ofthe diameter (Guerin-Franiatte, 1966: 3 19). There is also 

 one good example off. bairstowi in the Frodingham Ironstone: it is 

 a quarter whorl uncrushed fragment, wholly septate, with a whorl 

 height and breadth of 103.5 and 69.3 mm respectively, and is closely 

 similar to the Robin Hood's Bay holotype at the same size. 



Genus EPOPHIOCERAS Spath, 1924 



Epophioceras landrioti (d'Orbigny, 1849) 



1849 Ammonites landrioti d'Orbigny: 213. 

 1907 Ammonites landrioti d'Orbigny; Thevenin: 94, pi. 7, figs 4, 

 5 (holotype, from the Obtusum Zone, France). 



1966 Epophioceras landrioti (d'Orbigny); Guerin-Franiatte: 329, 

 pi. 217 (holotype). 



Range. Beds 446.5-448.11, Obtusum and Stellare Subzones; 3 

 specimens. A single Epophioceras sp. indet. was found in bed 446.4. 



Family ECHIOCERATIDAE Buckman, 1913 

 Genus PALAEOECHIOCERAS Spath, 1929 



Palaeoechioceras sp. indet. 



1973 Palaeoechioceras sp.; Getty: 9, pi. 1, figs 1 (BM C.79680), 

 5 (BM C.79678), 9 (BM C.79679); all from bed 467. 



RANGE. Bed 467, Simpsoni Subzone; 3 specimens. 



Genus GAGAT1CERAS Buckman, 1913 



REMARKS. In Robin Hood's Bay examples of Gagaticeras are 

 found only in beds 467^170, the top half of the Simpsoni Subzone. 

 Although they are divided here into G. neglectum with medium to 

 coarse ribs, G. finitimum with finer ribs, G. exortum with strongly 

 rursiradiate ribs, and G. gagateum with markedly depressed whorls, 

 larger collections of better specimens might suggest that there are 

 fewer than four species present. 



Gagaticeras gagateum (Young & Bird, 1828) 



1828 Ammonites gagateus Young & Bird: 255, pi. 12, fig. 7. 

 1876 Aegoceras gagateum (Young & Bird); Blake: 275, pi. 6, fig. 



8 (BM C. 17883, from bed 467). 

 1 880/82 Aegoceras gagateum (Young & Bird); Wright: 364, pi. 37, 



figs 8, 9 (BM C.2228, probably from bed 467). 

 1913 Gagaticeras gagateum (Young & Bird); Buckman: pi. 78 



(holotype, WM 104, from bed 467). 

 1919 Gagaticeras funiculatum Buckman: pi. 122 (holotype, BM 



C.41783). 

 1962 Gagaticeras gagateum (Young & Bird); Howarth: 102, pi. 



14, fig. 6 (WM 744, paratype of Ammonites multanfractus 



Simpson, 1855). 

 1976 Gagaticeras gagateum (Young & Bird); Schlegelmilch: 



138, pi. 21, fig. 7 (WM 104). 



RANGE. Occurs only in bed 467, Simpsoni Subzone; 2 specimens; 

 has strongly depressed whorls. 



Gagaticeras exortum (Simpson, 1855) PI. 2, fig. 7 



1855 Ammonites exortus Simpson: 44. 



1855 Ammonites integricostatus Simpson: 46. 



1910 Echioceras exortum (Simpson); Buckman: pi. 19, figs 2, 3 



(neotype (designated Howarth, 1962: 106), WM 645). 

 1912 Androgynoceras integricostatum (Simpson); Buckman: pi. 



47 (holotype, WM 92). 



RANGE. Beds 467-70, Simpsoni Subzone; 15 specimens; charac- 

 terized by markedly rursiradiate ribbing. 



Gagaticeras neglectum (Simpson, 1855) 



PI. 2 fig. 6 



1855 Ammonites neglectus Simpson: 45. 



1914 Parechioceras neglectum (Simpson); Buckman: pi. 101 



(holotype, WM 98). 

 1976 Gagaticeras neglectum (Simpson); Schleglemilch: 138, pi. 



21, fig. 8 (WM 98). 



