86b YORKSHIRE TYPE AMMONITES— II Nov. 



86. AMMONITES NITIDUS, Young & Bird 

 (Plate LXXXVI) 



Original Description 

 [Young & Bird, 1828, p. 256] 



" In the same beds [as A. cornucopia], we find a small ammonite 

 exactly shaped like No. 8, [A. cornucopia], but little more than an inch 

 in breadth, and quite smooth, marked only with lines of growth, a few 

 of which rise in sharp rings. This rare species may be named A . nitidus.— 

 It is evidently not the young of A. cornucopia ; for the latter is found 

 marked as the larger shells, but of a remarkably globose shape ; a peculi- 

 arity observed also in the young of several other ammonites." 



Remarks 



Proportions, 27, 35, 40, 38 ; subplaty-, pachygyral, latumbilicate. 



Stages, conch, serpenticone ; periphery, 1 ; ornament, 4. 



The rings are irregular in size and distance ; they have a distinct 

 backward trend after they leave the rounded undefined inner margin. 



What is seen undamaged is all body-chamber ; part of L* is visible 

 and appears to be somewhat simple. Earlier whorls are possibly striate 

 or smooth. 



Genus, Trachylytoceras, now II, vii ; family Lytoceratidae. 



Geological position according to Simpson, 1884, 70, Jet Rock, 

 Hawsker shore. 



Result 



Trachylytoceras nitidum, Young & Bird sp. 1828, Whitbian, 

 [exaratum zone, Hawsker, near Whitby] 



