Vol. 70.] DEVELOPMENT OF TRAGOPHYLLOCERAS LOSCOMBT. 343 



The change of whorl-shape with increase of diameter is illustrated 

 in Table I (p. 342). The specimens came partly from 10 feet above 

 the Belemnite-Stone on Black Yen (Xos. 1, 3, -A, 6, 11, & 20), and 

 partly from the horizon of the Upper Limestone (Xos. 2, 5, 7, 9, 

 & 19) : the remaining specimens were not collected in place, but 

 they also came, of course, from the Green Ammonite Beds of Black 

 Yen and Stonebarrow. With the exception of the three ornamented 

 specimens (13, 14, & 17), of which I shall have to speak again later, 

 there is a very regular decrease in thickness and size of the umbilicus ; 

 and, as a comparison of Table I with the dimensions of adult speci- 

 mens given in Table II (below) will demonstrate, the characters of 

 the typical form already are present at a diameter of 2o mm., 

 whereas specimens measuring between 10 and 20 mm. still have a 

 slightly larger umbilicus and are a little thicker. 



With regard to Table II, which deals with adult forms, it is 

 a matter for regret that, on account of the unsatisfactory mode of 

 preservation, no large specimen could be developed back to the 

 protoconch. But. as a comparison of the dimensions, and especially 

 the development of the suture-line, will show, there can be no doubt 

 concerning the connexion of the small pyritized casts with the large 

 calcareous shells so commonly found as body-chambers only. 



Table II. 





Diameter 



Height. 



Thicl 



Uml/Uirvs. 





in millimetres. 



Percent. 



Per cent. 



Per cent. 



1 . Sowerby's type 



78 



54 



23 



13 



2. Wright's figs. 4 & 5, pi. xl ... 



148 



53 



?23 



14 



3. Pompeckj's specimen 1 



65 



52 



23 



14 



4. Specimen 919 a (Coll. Lang) ... 



94 



52 



26 



14 



5. Specimen 621 (Coll. Lang) ... 



98 



53 



25 



13 



6. Spec. 1390 (Coll. F. H. Butler \ 



78 



54 



23 



13 



7. B.M. 90 (Coll. De la Beche) ... 



48 



52 



F25 



?12 



8. B.M. C.3719 (Coll. Beckles) ... 



77 



P55 



— 



rll 



9. B.M. C 12609 (CoU. H. S. 



109 



52 



24 



12 



Bomer). Seatown. 











10. B.M. C7301 (Coll. Slatter). 



95 



53 



26 



13 



Golden Cap. 











11. B.M. C6731 (Coll. 1 ! Slatter). 



53 



: : 54 



P23 



:-i2 



Little Wolford. Warwickshire. 











12. B.M. C 12633 (Coll. Watson). 



6Q 



55 



24 



11 



Xapton Hill. 











13. From Belemnite-Stone (Coll. 



53 



52 



22 



14 



Lang). 











14. D'Orbigny's specimen (text)... 



90 



55 



25 



10 



14a. do. (fig.) 



92 



54 



24 



13 



15. B.M. 37181 (Coll. Tesson). 



69 



55 



25 



13 



Vieux Port, Calvados. 











16. Pompeckj's specimen 3. 



67 



55 



26 



12 



Sables, near Bayeux. 











Specimens 1-7 & 13 come from the Lyme Regis district. The locality of 

 No. 8 is unknown. No. 11 represents a slightly crenulated. probably low- 

 zonal variety. 



