99b YORKSHIRE TYPE AMMONITES— II Mar. 



99. AMMONITES SUBTENSIS, Bean 

 (Plates XCIXa, b) 



Original Description 

 [Leckenby, Q.J.G.S., xv, 1859, PP- 7> IO 



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



Ammonites Arduennensis, D'Orbigny. 



" [P. 10.] 10. Ammonites Arduennenis (?), D'Orbigny. 



" Ammonites subtensis, Bean, MS. 



" The ribs are much more delicate and numerous than in D'Orbigny 's 

 figure, but there are no other distinctive features. 

 " Locality. The Castle Rock, Scarborough. 



Remarks. 



There are 3 specimens in the Sedgwick Museum, Cambridge 

 (Leckenby Coll.), with original labels, presumably Leckenby 's MS, 

 " Am. subtensis, Bean, Kel. Rock, Scarboro' Castle." To the largest is 

 added " very large ex." To the smallest " attains 7 in. diameter." 

 There is another specimen in the Whitby Museum, No. 1382, labelled 

 " Am. subtensis." All these, but certainly the three from Cambridge, 

 may be regarded as Bean's syntypes. It seems advisable to take the 

 largest as the lectotype. 



Subplaty-, sublepto-gyral ; perlatumumbilicate. 



Stages, conch, serpenticone ; periphery, 1 ; ornament, 4 to 5* to 

 almost 5**. 



The ornament is regular versiradiate costae which bifurcate about 

 the middle of the lateral area, with occasionally one entire. About 

 75 mm. diameter furcation tends to disappear, and less numerous single 

 ribs, each ending in a spine, are developed ; later, ribs fail in middle 

 lateral area, when there are spines on peripheral border and swellings 

 on inner area. 



Periphery in first stage regularly costate ; in second, distantly costate 

 with smaller intermediate costae, relics of the last furcate ribs ; in third 

 stage, smooth. 



Suture-line, L 1 large, feebly tripartite ; L 2 ,V all very small, forming 

 hanging umbilical lobe which is barely as long as L 1 . 



Genus Peltoceras, Waagen ; family Aspidoceratidae. 



The position of the furcation separates it from Am. arduennensis, 

 d'Orbigny, and from many other species. Geological position, " Kelloway 

 Rock " of Leckenby. The large specimen is much ironstained, and is 

 from a brown calcareous matrix with distinct iron grains and some irony 

 sand. The smaller example from a grey calcareous oolitic matrix (See 

 S. Buckman, Q.J.G.S., 1913, 154). 



Result 



Peltoceras subtense, Bean sp. 1859, Callovian, athlcta zone, 

 The Castle Rock, Scarborough. 





