121b YORKSHIRE TYPE AMMONITES— II Mar. 



121. AMMONITES LONGvEVUS, Bean, err. Leckenby 

 (Plates CXXI a, b) 



Original Description 

 [J. Leckenby, 1859, pp. 7, 11] 



" [P- 7] Fossils of the Kelloway Rock of Yorkshire .... Am. 

 Lamberti, Sowerby. 



" [P. it] 19. Ammonites Lamberti, Sowerby. 



Ammonites longcevus, Bean, MS. 



This Ammonite approaches Am. flexicostatus, but in fiexicostatus there 

 are two or three smaller ribs between each principal one ; whereas, in 

 Am. Lamberti, they simply bifurcate, and are much less incurved than 

 in the former species. 



" Locality. The Castle Rock, Scarborough. 



Remarks 



Four specimens in the Sedgwick Mus., Cambridge, (Leckenby coll.) 

 bear on back of tablet an original label (Leckenby's writing ?) " Am. 

 longaevus (Bean), Scarboro , Kel. Rock." The largest example also bears 

 a label " Am. longaevus Bean MSS." and this may be taken as lectotype. 

 The others are distinct : see below. 



Proportions, 51, 47, 33, 15 ; perplaty-, subpachygyral ; angust- 

 umbilicate. 



Stages, conch, platycone ; periphery, ic, passing from 2 (2c ?) ; 

 ornament, 4. 



Ribs strongly prorsi-arcuate — in form of a bow falling forwards — 

 regular, bifurcate ; place of bifurcation varies ; rarely there is an inter- 

 mediate pair without corresponding primary : see fig, marked in white 



The ribs pass with forward arching over periphery, which becomes 

 more inflated with age. Umbilicus small, without recession. 



Genus, LONGiEVICERAS, nov. p. xiv ; family, Cadoceratida?, Hyatt 

 1900. 



Geological position : from a bed of Leckenby's Kelloway Rock, 

 matrix brown, somewhat sandy, occasionally oolitic (S. Buckman, 1913, 



154)- 



Result 



Lonceviceras loncevum, Bean cit. Leckenby 1859, Callovian, 

 athleta zone, Scarborough, Yorkshire. 



Note 



The other three syntypes, all much about the same size, presumably 

 adults as they show body-chamber and umbilical expansion, differ from 

 Am. longav.is (lectotype) '. — Ribs feebly arcuate, nearly coincident with 

 straight line (versiradiate), bifurcation variable as to position and irregular 

 in degree — a regular sequence of one long and one short, the latter due 

 sometimes to furcation, sometimes to intercalation ; periphery sharper 

 and its ribs with apex of V less rounded. 



Matrix, greyish-brown, rather finely oolitic. Dimensions of figured 

 specimen, 35, 46, 26, 19 ; about half-whorl body-chamber. Gen. and 

 spec, nov., Pseudocadoceras boreale, [Callovian, kamigi-zone], Scarborough, 

 Yorkshire, PL CXXI b ; Holotype. "" See Cadoceras, sp. nov., S. Buckman, 

 Q.J.G.S., LXIX, 1913, 154, 162. 



