xvi INFERIOR OOLITE AMMONITES. 



II. Genus — Chartronia, 1 S. Buckman. 



(Type : Chartronia hinodata, sp. n.) 



Definition. — Stenogyral, latumbilicate, binodate, versi-rectiradiate, septi- 

 carinate, 2 subornatilobate. 



Note. — The binodation is a phase of development. There might be uninodate 

 ancestors and descendants of the type-species, and yet they would belong to 

 the same genus. 



Remarks. — The nodi of the inner row are situated at some little distance from 

 the edge of the inner margin, and there are costse extending from them to the edge 

 of that margin. The nodi of the outer row are rather inconspicuous ; they are 

 situated on the edge of the periphery, just beyond L. (superior lateral lobe). 



Distinction. — The binodation distinguishes the genus from either Lillia or 

 Haugia. The more ornate character of the suture-line separates it from Lillia. 

 It may also be noted that the position of the inner row of nodi is different from 

 anything found in Lillia or Haugia. 



1. Chartronia binodata, S. Buckman. Suppl., Plate I, figs. 11 — 15. 



Description. — Given in the definition of the genus. 



Note. — The peculiar characters of the species are, first, a row of tubercles set 

 rather away from the inner margin ; secondly, another row of small tubercles on 

 the edge of the periphery. 



Locality and Stratum. — Frocester Hill, Gloucestershire. Certainly from the 

 " Cephalopod-bed," and, judging by the matrix, from the strata containing 

 Dnmortierise. 



Date of Existence. — Hemera Dumortierix presumably. 



History of the Figured Specimen. — Purchased from the collection of the late 

 Dr. Thos. Wright, F.R.S., &c. 



fauna changes quite independently of lithic conditions is shown throughout the Lias, particularly in 

 Dorset. 



It must be remembered that the fauna of any given hemera was of more than European exten- 

 sion, but that particular lithic characters were often excessively local, and seldom contemporaneous. 



1 In honour of M. L. Chartron, Memb. Soc. Geol. de France. 



2 This may be known by the impressed periphery bearing the mark of the partition-band. 



