1858.] LECKENBY ^KELLOWAY FOSSILS, YOEKSHIKE. 9 



gradations of form between it and Am. sublcevis, all of which in the 

 adidt shell become smooth and hardly distinguishable from each other. 

 Localities. Near Gristhorpe Bay, and at Eed Cliff. 



3. AMTvroyiTES bugosus, Leckenby. 



Gibbous, deeply umbilicated, ribs very thick and strong, sepa- 

 rated by wider spaces. Aperture rounded, indented one -fourth by 

 the succeeding whorl. 



Locality. Near Gristhorpe Bay. 



4. AifMois^iTEs GowEEiAirus, Sowerby. PI. I. fig, lor-ld. 



Young shells much resemble Am. Calloviensis, but in the adult 

 the ornamented square back becomes rounded in this species. 



5. Ammonites eeyeesus, Leckenby (Simpson, MS.). PI. I. fig. 2. 



Discoid; of shght volutional increase, back rounded, ribs very 

 sharply defined, bifurcating at the middle of the whorl, and then 

 bending very decidedly from the aperture. Occasionally an entire 

 rib is introduced. Aperture rounded. Scarcely indented by the 

 succeeding whorl. 



Locality. The Castle Bock, Scarborough. 



6. Ammonites YEETTiiOf us, Leckenby (Bean, MS.). PI. I. fig. Sa, 36. 



This Ammonite appears to approach most closely to Am. Marice, 

 D'Orb. ; the ribs are strong and cord-Hke, forming coarse folds on 

 the back. 



Locality. Near Gristhorpe Bay. 



7. Ajoionites Pocuxtjm, Leckenby (Bean, MS.). PI. I. fig. 4a, 



46, 4c. 



Discoid; sides flattish, back rounded, ribs prominent near the 

 inner margin, dying out before they reach the back, where their 

 place is supplied by numerous slender ones, which pass uninter- 

 ruptedly across it. In some specimens the ribs near the inner 

 margin are so strong as to become tubercular. Aperture circular, 

 slightly indented by the succeeding whorl. 



Locality. Near Gristhorpe Bay. 



8. Ammonites Chatjviniantjs, D'Orbigny. 



I have referred this Ammonite to Am. Chauvinianus on the 

 authority of Dr. Oppel, who identified it without hesitation. 

 Locality. The Castle Rock, Scarborough. 



9. Ammonites alligatus, Leckenby (Bean, MS.). PL II. fig. 2a, 2b. 



Discoid ; sides flatted, especially in the adult ; back gently rounded ; 

 ribs numerous, entire on the sides of the whorl, bifurcating across 

 the back ; volutions deeply constricted at intervals, as in A. rotula 

 and other species. Aperture subquadrate, scarcely indented by the 

 succeeding whorl. 



Localities. Near Gristhorpe Bay, and Scarborough Castle Rock. 



