93b YORKSHIRE TYPE AMMONITES— II Jan. 



93. AMMONITES ELEGANTULUS, Young & Bird 

 (Plate XCIII) 



Original Description 

 [Young & Bird, 1828, p. 267.] 



No. 11, PI. XIII, is another of this family, corresponding with 

 Sowerby's A. elegans, Tab. 94. 1. It is thin, slender ribbed, and has 

 the inner angle of the whirl truncated, the truncated part generally 

 forming a concave surface, like the groove in A. angulatus. — We have 

 a minute shell nearly corresponding with this, but having the inner angle 

 less raised, and the interior whirls a little more displayed. This neat 

 little species, which is not the young of A. elegans, the latter being found 

 of the same size along with it, may be termed A. elegantulus. 



All these sigmoidal Ammonites are keeled. 



Remarks 



Proportions, 37, 49, 28, 24 ; perplaty-, subpachy-gyral, sub- 

 angustumbilicate. 



Stages, conch, platycone ; periphery, 3 (3c ?) ; ornament 4, 3, 2. 



From a rounded peripheral edge and from a low concave inner 

 margin the whorl rises to an obscure median ridge ; there is consequently 

 a depressed or flattened area around the umbilicus on the inner half of 

 the whorl. The ornament consists of small, rather clean-cut ribs of 

 low relief, which diminish in size and in the end pass to a striate stage. 

 The ribs in the inner whorls are somewhat distantly spaced, so that an 

 earlier form with distant costae may be expected. 



The carina is distinct, not very prominent, rather thin. It is 

 presumably septate. The specimen is nearly complete : there is about 

 half a whorl body chamber, as shown by the broken part. 



Genus, Elegantuliceras, nov. (II, viii) ; family Hildoceratidae. 



Geological position, " U.L. 7 [Jet Rock]," Simpson, 1884, 108. 



Result 

 Elegantuliceras elegantulum, Young & Bird sp. 1828, 

 Whitbian, exaratum zone, near Whitby. 



