﻿250 INFERIOR OOLITE AMMONITES. 



identified, and which must be excluded as belonging not only to different species, 

 but to different genera. The synonyms given at the heading of this article will 

 further supplement this list by indicating which species described, under other 

 names must be united under the name "radians." 



Under the name Am. rudiosus Dumortier (loc. tit.) gave figures of two speci- 

 mens, one of which (figs. 3, 4) is practically identical with Reinecke's figure of 

 Am. radians. The only difference observable is that the aperture of fig. 4 is 

 longer and more compressed. Most of my specimens show the same difference ; 

 but the value of this difference is diminished when it is remembered that Bum. 

 radians was, like the other species of the genus, gradually assuming a more and 

 more elliptical whorl. The elliptical whorl, therefore, is merely a sign of progress ; 

 and, further, much depends on where the section of the whorl is taken. How 

 great a difference half a whorl may make in this matter is amply illustrated by 

 PI. XLII, figs. 2, 14. 



Branco 1 recognised that Durnortier's Am. radiosus was not the same as 

 Seebach's, and he bestowed the name " H. pseudoradiosum " on fossils of which he 

 gave a figure, while he quoted Durnortier's figures in the synonymy ; but Branco's 

 figures do not agree with Durnortier's (see p. 246). 



Haug also recognised that Durnortier's figures did not represent Seebach's 

 Am. radiosus; 2 and he consequently bestowed a new name, " rhodanica." This 

 name must now fall as one of the synonyms of " radians." 



According to my interpretation Bumortieria radians is very variable ; the size 

 and distance of the ribs, the amount of inclusion of whorl, and the compression of 

 the whorl giving rise to great variety of form. As the immediate progenitor of 

 this species — say Bum. Levesquei — possessed widely-separated ribs, therefore such 

 ribs are to be found in the inner whorls of Bum. radians. In fig. 1 , and in fig. 8, 

 PI. XLII, it may be seen that they are superseded at an early date by the finer 

 and closer ribbing — the ribbing of " radians." Fig. 11 of the same plate is again 

 a rather abnormal form, wherein the coarse ribs are continued to the end, but 

 only after a period of finer ribbing. 



The compression of the whorl varies considerably, as may be seen by 

 comparing PI. XLII, figs. 7 and 10; and the shape of the whorl varies very 

 much in the same specimen. The more developed the specimen the more com- 

 pressed is the whorl ; and figs. 3 and 6 show that the compressed specimens not 

 only have finer ribbing, but have superseded the coarse ribbing — the ancestral 

 character — at so early an age as to almost obliterate it. 



That Bmnortieria radians is descended from Bumortieria Levesquei there can 

 be little doubt ; and Dr. Haug says that intermediate forms bind the two species 



1 " Untere Dogger ;" ' Abh. z. geol. Spez.-Karte von Elsass-Lothringen,' Bd. ii, p. 77, 1879. 



2 'Ueber Polymorphidae ;" ' Neues Jahrbuch far Mineral., &c.,' Bd ii, p. 138, 1887. 



