THE AMERICAN NA TL T RAUST. [Vol. XXXVII. 



sist. Some of the early Svcotypus developed echinations by an 

 accentuation of the tubercles, but these did not prove successful. 



Hemifusus and Melongena represent the spinous line among 

 the Fusidae, which seems to have been equally successful with the 

 non-spinous line of Fusus proper. In such types as Hemifusus 

 colosscus, a strong line or spiral persists for a time after the tuber- 

 cles have become obsolete. This I have formerly spoken of as 

 a keel, but it represents merely the natural transition from tuber- 

 culous to round stage. A similar faintly carinate shoulder angle 

 occurs again in most cases, before the spines appear. 



In company with Fu/^ur maximum is a variety (var. A of Con- 

 rad) in which spines are found on the 

 last whorl. These spines are a new 

 feature and are not to be confounded 

 with the tubercles of the earlier 

 whorls. The latter are the ren 

 of the ribs on the shoulder angle, 

 while the spines are periodic emargi- 

 nations of the lip on the line of the 

 shoulder angle. In the early suc- 



come in earlier and earlier, hiving the 



the whorls. Fitlgur iritouis Conrad 

 (Fig. 14) is a type from the Mid- 

 Miocene of Yorktown, Va., in which 

 spines appear after a short period of a round-whorled condition. 

 The spines gradually increase in size until thev are equal to those 

 of the modern F. caricum. Two branches are met with here : 



