222 The Lineage of Tragophylloceras loscombt. 
seventh suture in T. loscombi the first lateral saddle is greater 
than the external saddle, a characteristic feature in the sutures 
of Tvagophylloceras, yet this is not attained in type I until 
much later. In this form, moreover, the first indications of 
denticulation appear at a diameter of 4 mms., while in loscombi 
they are developed at little more than half this diameter.* The 
stage reached by the latter form at 4 mms. is not attained by 
type I until the diameter is 7 mms. 


G Reach 
(Thiea ) 
b 
(Serona) 
a 
CFiret ) 
Fy Sutheat dute pment of fermen 
4 
Ghore 4g! 
(4 mm) 
33 Sat | THe h. 
( 30mm) 

Ka & 
The suture shown in fig. 3 is from a rather more advanced 
form belonging to type 2. That shown in fig. 4 was drawn 
from an isolated piece of a whorl and thus its exact position 
in the series cannot be given, but it is at approximately the 
diameter of 30 mms. and it is closely paralleled by Spath’s 
figure of loscombi at two thirds that diameter. It is also 
practically identical with the suture figured by Quenstedt7 as 
Ammonites heterophyllus numismalis. 
The differences between the relative heights of whorl and 
se 
* Toc: city shiga lide ps 34 
+ Quenstedt, F. A., ‘Amm. Swabisch. Jura.’ Tab. 37, fig. 10, 1883-5. 
Naturalist, 
