142 INFERIOR OOLITE AMMONITES. 



Hildoceeatimi {continued). 



Genus — Hadgia, 8. Buckman, 1888. 1 



(Type — Haugia variabilis, cTOrligny, sp.) 



Definition. — Discoidal, with a strong hollow-carina ; whorls ornamented with 

 arcuate, 2 or subsigmoidal, ribs, and sometimes with knobs on the inner marginal 

 edge; from these knobs two, three, or more ribs spring. Ventral area not 

 actually denned ; it is rounded when the test is absent, but otherwise furnished 

 with a strong hollow-carina (Plate A, fig. 38). Inclusion variable ; inner margin 

 convex. Suture-line (Plate A, figs. 34 — 37) possesses a large, somewhat branched, 

 superior lateral lobe, a narrow, deep, superior lateral saddle divided by a medium- 

 sized accessory lobe, an inferior lateral lobe about half the size of the superior 

 lateral, inferior lateral saddle not nearly so deep as superior lateral causing the 

 inferior lateral lobe to appear one-sided, auxiliary lobes more or less drooping. 



Remarks. — The species which are included in this genus show a very obvious 

 relationship, and yet exhibit a certain amount of progress in development. The 

 following features are the most characteristic : 1st, the strong, very large hollow- 

 carina ; 2nd, the high, but much compressed, whorls ; 3rd, the broad, much 

 ornamented, and therefore highly-developed, superior and inferior lateral lobes — 

 which, too, occupy nearly the whole side, and the small, unimportant, and 

 therefore undeveloped, auxiliary lobes, which are cramped up at one end as if of 

 no account. 



The members of this genus belong apparently to two more or less parallel 

 series, both of which become more involute as they develop. The first are 

 characterised by possessing arcuate ribs generally, and knobs on the inner margin ; 

 the second — probably the younger and more developed branch — do not possess 

 any knobs, and their ribs are inclined to become subsigmoidal. Thus these latter 

 apparently possess the characters of the adults of the first (whose knobs disappear 

 in the last whorls), combined with greater involution generally. 



The following species belong to the first class : — Haugia variabilis (d'Orbigny), 

 E. Ogerieni (Dumortier), H. navis (Dum.), H. malagma (Dum.), H. illustris 

 (Denckmann). To the second belong: — Haugia Eseri (Oppel), H. occidental-is 

 (Hang). 



1 See p. 45. 



2 Ribs which run nearly straight across the lateral area, and are only slightly projected on the 

 ventral area. Thus they are arched like a half-expanded bow, each end projecting towards the 

 front about equally. 



