HAUGIA. 145 



which nevertheless belong to two different genera, should be found located in 

 almost the same horizon as the type-species of this genus. These species are 

 Hammatoceras insigne (Schubler), and Graminoceras dispansum (Lycett), which 

 occur together in the upper part of the Striatulum-subzone ; while Haugia 

 variabilis occurs, in the Cotteswolds, in the Sands below (see Section vi, p. 45). 

 Gramm. dispansum was considered by Dr. Wright to be a variety of Haugia 

 variabilis ; on this point I shall have more to say presently. 



The species of this genus all belong to the Upper Lias, and are mostly confined 

 to Gloucestershire, where they are characteristic of the Cotteswold Sands and 

 Striatuhim-heds. The only reason for including them in the present work is that 

 only one, Haugia variabilis — on which, too, I can give some additional information — 

 has been figured and described by Dr. Wright in his ' Monograph on Lias 

 Ammonites ;' and that I have thought it an advantage to give a complete account 

 of the species associated with it (see also p. 113). 



Postscript. — At page 141 I suggested that Haugia was possibly descended 

 from Lillia. The time which has elapsed since the publication of that page has 

 enabled me to more fully consider this point ; and I have concluded that my 

 surmise is quite correct. The backward-directed ribs, noticeable in the immature 

 Haugia variabilis, are to be seen in the mature Lillia ; the broad ventral area and 

 quadrangular whorls of the young H. variabilis are also characteristic of Lillia ; 

 the knobs on the inner margin, which are very irregular in Lillia, are more 

 regular in Haugia^ and in the higher species die out only because the side 

 becomes broader ; finally the suture-line, which in the young (Plate XXVIII, 

 fig. 3) has much resemblance to that of Lillia, exhibits, when adult (Plate A, 

 figs. 34 — 37), a development in the ornamentation of the superior and inferior 

 lateral lobes and the commencement of extension in the matter of auxiliaries. 

 All the changes here enumerated are what we might expect to accompany the 

 development of involute, high, compressed whorls instead of evolute, sub-quad- 

 rangular whorls. Practically no trace of the sulcate ventral area of Lillia remains 

 in the young of Haugia — the uncarinate stage (Plate XXVIII, figs. 1, 2) passes 

 into a carinate stage with flat ventral area — the sulcate stage is therefore omitted. 

 A similar omission is seen in the higher forms of Haugia, where the tubercled 

 stage is entirely wanting. We may sum up the development of Haugia as 

 follows : — Increase of compression, increase of involution, decrease of ribs (almost 

 to extinction), decrease of knobs to total extinction. Just as the young of 

 Haugia variabilis exhibit the chief characters of the adult of Lillia, so even the 



^ The irregular ornameutation of the lower Haugice, namely, H. navis and H. malagma, which 

 caused Dumortier to place them in his section Podagrosi — the chief members of which belong to the 

 genus Lillia — should also be considered in this connection. 



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