HAUGIA ILLUSTRIS. 153 



From H. variabilis its small carina, small umbilicus, and ventrally projected 

 ribs easily separate it. 



Plate XXIII, fig. 16, gives tbe side view of a nicely -preserved small specimen 

 obtained from the Cotteswold Sands, North Nibley (Bed 18). This side view 

 shows the characteristic subsigmoidal ribs, differing from those of fig. 14. Fig. 17 

 illustrates the front view, and the size of the carina. In Plate A, fig. 36, is 

 depicted the suture-line of this specimen; and it is noticeable that the inferior 

 lateral lobe is larger in proportion than in the suture-line of H. jugosa. All 

 the figures of this species in these two plates were alluded to under the incorrect 

 name of H. Ogerieni. 



Haugia ILLUSTRIS {Denchniann). Plate XXVI, figs. 3 — 5. 



1844. Ammonites variabilis, d'Orhigny. Pal. Fran?., Ceph. Jurass., pi. cxiii, 



figs. 5, 6 (non 1 — 4). 



1887. — (Hammatoceeas) illusteis, Denckmann. Fauna Ob. -Lias 



Doerntea ; Abh. geol. Specialkarte von 

 Preussen und den thiiringischen Staaten, 

 Band viii, Heft 2, pi. v, fig. 2 ; pi. vi, 

 fig. 1 ; pi. X, fig. 5 (pi. iii, fig. 6 ?). 



Discoidal, compressed, hollow-carinate. Whorls much compressed, orna- 

 mented with arcuate ribs which spring from tubercles on the edge of the inner 

 margin. Ventral area not defined, bearing a large hollow carina. Inner margin 

 distinct, slightly sloped. Inclusion nearly two-thirds. Umbilicus small. 



The material at present in my possession is so very scanty and poorly 

 preserved that the characters of this form cannot be set forth in detail. It is 

 obvious that it is nothing more than a mutation of -ff. jugosa, and its position — one 

 stage higher, namely, in the Striatulum-heds — fully accords with this idea. As a 

 mutation of H. jugosa it has acquired greater compression and a smaller umbilicus, 

 but retains the knobs ; and thus it differs from H. Eseri, which has acquired greater 

 involution but not so much compression, and has lost the knobs. 



Haugia illustris is extremely scarce. It occurs in the Striatulum-heds, that is, 

 a stage later than the other tubercled species of the genus. I have collected it at 

 Penn Wood and Coaley Wood, Gloucestershire. Denckmann says {op. cit., p. 75), 

 " Am. illustris tritt ausserordentlich haufig in den Geoden unter der Bank mit 

 Am. striatulus auf, und ist fiir dieselbe leitend." 



Some specimens collected from Coaley Wood (Bed 13, p. 45) and from North 

 Nibley (Bed 20, p. 46) should possibly be referred to this species, but their pre- 



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