46b YORKSHIRI-: TYPE AMMONITES Eeb. 



46. AMMONITES HETEROGENES, Young & Bird 

 (Plate XLVI) 



Original Description 

 [Young & Bird, 1828, pp. 263, 264, 359. J 



" One of the most singular of all our ammonites, is that figured, 

 PI. XIV, No. 7 ; the outer whirl of which, has also two rows of knobs. 

 The interior part of the shell is comparatively flat, with ribs rather 

 prominent, and flattened on the back, very much like those of A. macu- 

 lalus : near the outer whirl, the ribs begin to have two slight knobs 

 on the sides ; and on that whirl, the ribs grow depressed |p. 264] and 

 the knobs elevated, making two prominent rows, as is sometimes the 

 case in the outer whirls of the A. perarmatus in the oolite, formerly 

 noticed. But the most remarkable circumstance to be stated is, that 

 the last part of the outer whirl suddenly swells to a great thickness, 

 as if it had belonged to another shell ; the difference being the more 

 striking, as the ribs in this part, instead of being flattened on the back, 

 are each split into three, at the outer row of knobs. The mouth, as in 

 the last species \A. heptangiilaris], is subpentangular. We may name 

 this singular shell A . heterogencs. Having examined three specimens, 

 all agreeing in form, we are fully satisfied, that it is not. as we at first 

 suspected, two different ammonites accidentally combined. The interior 

 whirls are much more displayed than in No. i [.1. heptangiilaris]. 



" [P- 359] Plate XIV. Fig. 7. A. heterogenes. Alum shale." 



Remarks 



Stages, conch, serpenticone, incipiently sphrerocone ; periphery, i ; 

 ornament, 4 and 5**. 



Genus", Androgynoceras, Hyatt 1867, (Gen. Hi) and family Liparo- 

 ceratidie. Geological position according to Simpson (1884. 104) " L.L., 

 I-' ... It occurs in the same beds with A. maculatus." 



Result 



Androgynocer.\s heterogenes, Young & Bird sp. 1828. |Char- 

 mouthian, striatum zone, near Whitby.] 



