﻿HUDLESTONIA SERRODENS. 229 



Hudlestonia affinis, it is quite possible that Braims' specimen may be, to a certain 

 extent, intermediate. 



There seems to be some indication of such facts in the specimens now before 

 me. The large fragment from Penn Wood, Gloucestershire (PL XXXVIII, fig. 1), 

 is certainly somewhat more gibbous than the specimens from Yorkshire, and 

 possibly more umbilicate. Whether it be actually more umbilicate than Seebach's 

 specimen, it is really impossible to say with such material. 



The great difference which exists between the young and the adult of this 

 species, as shown in the Yorkshire specimens (fig. 4), is a point well worthy of 

 notice. The young, of course, represent the ribbed stage of Hudl. Sinon, only that 

 their ornaments are finer altogether ; and presumably these ornaments were lost at 

 a much earlier age. The young, however, show that Hudl. affinis and Sinon 

 were derived from the same source, but that the former is rather more developed 

 — it assumes the senile characters at an earlier age. I do not derive Hudl. affinis 

 directly from Sinon, because Hudl. Sinon does not seem to foreshadow the gibbous 

 whorl of Hudl. affinis ; but it is unsafe to say much with such poor material. The 

 outer whorls of Hudl. affinis show the connection with Hudl. serrodens. 



The Dumortieria-beds (Jurense-zone) of Penn Wood, near Stroud, have yielded 

 the large fragment depicted in outline. The " Yellow and Grey Sands below 

 Dogger " of Blue Wyke, Yorkshire, have afforded Mr. Hudleston other examples, 

 which he has kindly sent me for examination. They are smaller and rather 

 thinner than the Gloucestershire fragment, and hence may be considered slightly 

 transitional to Hudl. serrodens. 



PI. XXXVIII, fig. 1, is the outline of a very poorly preserved fragment, and 

 its sectional view is shown in figs. 2 and 3. Fig. 4, showing the difference 

 between the young and adult of this species, is a specimen from Yorkshire ; fig. 5 

 is the front view of the inner whorls, and fig. 6 is the outline of the aperture of 

 the outer whorl. In figs. 7 and 8 are two views of a young example, which has 

 had to be more or less restored to show its true characters. 



Hodlestonia serrodens {Quenstedt). Plate XXXVIII, figs. 9 — 12. 



1846. Ammonites serrodens, Quenstedt. Ceph., pi. viii, fig. 14. 



1858. — — — Der Jura, pi. xl, fig. 6, p. 282. 



1866. — affinis, Brauns (non Seelach). Die Stratigr. und Pal. des S.-O. 



Theiles der Hilsmulde ; Palaeonto- 

 graphica,xiii, pi. xxv, figs. 1, 2, 4 (3?). 



1866. — — Schloenbach (non Seebach). Jurass. Armn. ; Palaeon- 



tographica, xiii, pi. xxviii, fig. 1. 



