HAUGIA VARIABILIS. 147 



on the top of the inner margin. Ventral area ill-defined, convex, and carrying a 

 large hollow carina, slightly sulcate laterally. Inclusion variable. 



No specific name has been more misused than this. It may truly be 

 said that under it have been included all the species of Haugia, several of 

 Grammoceras, and even some other species belonging to genera still more remote. 

 As now restricted in this Monograph, the species is but little variable ; but there 

 are two chief forms which are easily separable from one another. They may be 

 mentioned as follows : 



I. The type as figured by d'Orbigny and Chapuis et Dewalque, loc. cit. 



II. Var. a has very coarse, irregular ornamentation (Wright's ' Lias Ammonites,' 

 pi. Ixviii, but sometimes more involute). 



Specimens agreeing exactly with the type have not apparently been found in 

 England, unless Dr. Wright's figs. 5, 6 in pi. ixvii belong to it.^ The form o, so 

 well delineated in that author's pi. ixviii, is remarkable for its coarse irregular 

 knobs, and for the absence of a well-marked space between the inner margin and 

 the knobs, as seen in d'Orbigny's figure; in one of my specimens this is much 

 more marked than in Dr. Wright's — in fact the knobs almost touch th? inner 

 margin in the inner whorls. 



When I wrote the explanation of Plate XXIII I included in this species 

 certain specimens which should come under the designation Haugia jugosa (see 

 that article, p. 149). I made this mistake because they are so much commoner 

 than the true Haugia variabilis, of which I had not thoroughly learnt the 

 peculiar characters. I consider that the chief points peculiar to Haugia 

 variabilis are — 



1. The ribs directed backwards until an advanced age. 



2. The narrow whorls. 



3. The open umbilicus. 



4. The slow increase in diameter. 



5. The more irregular ornamentation. 



The backward direction of the ribbing is a fact upon which particular stress 

 may be laid. The same feature may be noticed in Lillia erbaensis and Lillia 

 tirolensis (Dumortier, ' Bassin du Rhone,' pis. xxiii and xxiv), and certainly sug- 

 gests the connection between Haugia and Lillia (see p. 145). 



Many species have passed under the name Arm. variabilis, and one of the best 

 known is Grammoceras dispansum. For the differences which separate it from 

 H. variabilis see the articles on the genera Haugia and Grammoceras (pp. 144, 

 161), and also the article on Gramm. dispansum (p. 212). 



The species from the Bradford-Abbas Inferior Oolite which were quoted as 

 Amm. variabilis belong to the genus Sonninia. 



1 See previous page, footnote 2. 



