10 ' PSOCEEDINGS OF THE GEOLOGICAL SOCIETY. [Mar. 24, 



10. Ammonites ARDtrEifNENSis (?), D'Orbigny. 

 Ammonites suhtensis, Bean, MS. 

 The ribs are much more delicate and numerous than in D'Or- 

 bigny's figure, but there are no other distinctive features. 

 Locality. The Castle Eock, Scarborough. 



11. Ammonites binattjs, Bean, MS. 



This Ammonite approaches Am. Bakerice, but the foliations of 

 the septa are much more simple, and in the adult the sides are 

 flatter. In some examples, the opposing ribs do not meet in posi- 

 tion on the back, but appear as if dislocated, and there is a flattish 

 space intervening. 



Locality. The Castle Bock, Scarborough. 



12. Ammonites Koenigi, Sowerby. 



This is one of our most abundant Ammonites. Perfect specimens, 

 5 inches in diameter, are not uncommon, and I have seen fragments 

 of individuals much larger. 



Localities. Bed Cliff, and Scarborough Castle Bock. 



13. Ammonites Athleta, Phillips. 



The inner whorls of this species readily distinguish it from A. 

 perarmatus. 



Locality. Castle Bock, Scarborough. 



14. Ammonites gemmattjs, Phillips. 



This is an abundant, but most variable species. Specimens, 

 5 inches in diameter, are not uncommon. It passes into Am. 

 Duncani by imperceptible gradations. 



Localities. Near Gristhorpe Bay, and Scarborough Castle Bock. 



15. Ammonites Gulielmi, Sowerby. 

 Ammonites Rowlstonensis, Young and Bird. 



This has also been an abundant and thriving Ammonite in the 

 CaUovian Sea. It is often marked in cabinets as Am. Calloviensis. 

 Localities. Near Gristhorpe Bay, and Scarborough Castle Bock. 



16. Ammonites Mureayanus, Simpson, MS. 



Discoid ; sides of the whorls flat ; their inner margins squarish, 

 of slow volutional increase, ribs slender, straight, with spines or 

 tubercles on the outer margin. An inner row of tubercles on the 

 outer whorl of aged examples. Aperture a parallelogram, more than 

 twice as long as broad; not indented by the succeeding whorl. 

 Diameter 12 inches ; greatest thickness |- inch. 



Locality. The Castle Bock, Scarborough. 



17. Ammonites placenta, Leckenby (Simpson, MS=). PL II. fig. 1. 



Slightly gibbous ; inner volutions nearly concealed ; principal ribs 

 curving regularly and gracefully towards the aperture, occasionally 

 bifurcating, but more frequently entire, with two or three shorter 

 ones introduced between them, which all pass over and form a ere- 



