I3b YORKSHIRE TYPE AMMONITES Mar. 



13. AMMONITES LYTHENSIS, Young & Bird 

 (Plate XIII) 



Original Description 

 [Young & Bird, 1828, pp. 266, 267.] 



"Another species, larger than the last [A. impendens], but smaller 

 than A. Mulgravius, has like it sigmoidal ribs, but less regular, and less 

 curved. A very small part of the inner whirls is displayed, and the 

 interior edge [p. 267] of each whirl being rectangular, the central part 

 appears like a small round pit, with perpendicular sides. To this species 

 we have given the name A. Lythensis." 



Remarks 



Stages, conch, oxycone ; periphery, 3c ; ornament, 4c. 



There is a septicarina, which is not prominent : the partition-band 

 is set on a rounded periphery, but the mark of the band is not very plain : 

 it can be seen in lower part of fig. 2. 



Genus Pseudolioceras, S. Buckman, 1888, 81, — family Hildoceratidse. 



Geological position according to Simpson, Alum shale, Upper Lias (i), 

 Peak (1884, 109). 



Result 



Pseudolioceras lythense. Young & Bird sp., 1828, Whitbian 

 [probably braunianum-zone], near Whitby. 



