lib YORKSHIRE TYPE AMMONITES Mar. 



7910 



II. AMMONITES BOULBIENSIS, Young & Bird 

 (Plate XI) 



Original Description 

 [Young & Bird, 1822, p. 252.] 



" [P. 251] No. 5, PI. XIII, also from the aluminous strata, appears 

 to be [p. 252] a small specimen of Sowerby's . concavtis, Tab. 94, fig. 2. 

 [A. subconcavus, 1828, see No. 10]. It has a faint spiral furrow 

 on one side. — We have another shell with the same kind of strong waved 

 ribs, but having the internal angles of the aperture sharp, as in No. 8 

 [A. mulgravius, No. 4]. This species, which is also from the alum 

 shale, and which is not figured, may be named a. Boulbiensis. 



Additional Details 

 Young & Bird, 1828, p. 267. — " To another shell [than A. Lythensis], 

 of which the umbihcus, or central cavity, has sloping sides, we have 

 given the name A. Boulbiensis. Its ribs are rather prominent, as in 

 A. subconcavus, of which it may possibly be a variety." 



Remarks 



Stages, conch, oxycone ; periphery, 3c ; ornament, 3c — about sub- 

 costate, really sort of semicostate or striicostate. 



The genus is Pseudolioceras, S. Buckman, 1888, p. 81. 



The geological position, Simpson says, is " U.L., i," (1884, 109). 



Result 



Pseudolioceras boulbiense, Young & Bird sp., 1822, Whitbian, 

 [perhaps braunianum-zone], near Whitby. 



