60 INFERIOR OOLITE AMMONITES. 



allied species. The variety Lioc. formosum closely resembles Ludtvigia cormi ; the 

 adult of Lioc. v-scriptum is somewhat like Lioc. fallax, while the young approach 

 Lioc. apertum ; the variety Lioc. pingue and the young of Lioc. giganteum are 

 somewhat similar. All these will be alluded to and explained under their respec- 

 tive headings. 



As regards the type form, if the character of its ribbing, the great inclusion of 

 its whorls, and the proportions shown by the figures, 1 be kept steadily in view, I 

 do not think it should be confounded with any other species. From Lioc. elegans 2 

 (Young) and Lioc. opalinum (Reinecke) its coarser ribbing and very concave umbilicus 

 separate it specifically ; from any forms of Eudwigia, the mode of ribbing and the 

 difference in the suture-line separate it generically. The more minute differences 

 which distinguish it from its varieties will be best understood by reference to 

 pp. 66, 67, 69. 



It is singular that in spite of the frequency with which this species occurs, yet 

 from the year 1815, the date which Sowerby's plate bears, until the year 1881, 

 when my father figured a variety of it, no approach to any correctly identified 

 specimens of Sowerby's species had been figured in England, nor, I believe, on the 

 Continent. The regularly hollow umbilicus, which is mentioned by Sowerby, seems 

 to have been either ignored or not noticed by those who have referred to this 

 species ; and, so far as my experience goes, the identification of this shell in both 

 public and private collections leaves much to be desired. The name Ammonites 

 concavus is given, for some reason, to a shell or a whole series of forms from the 

 Upper Lias, and seldom to our species from the Inferior Oolite. Probably 

 d'Orbigny and Dumortier are to a certain extent answerable for this. The form 

 from the Upper Lias figured by d'Orbigny under the name Am. concavus (' Terr. 

 Jurass. Ceph.,' pi. 116) is referred by Dr. Wright 3 to Am. Lythensis, Young and 

 Bird ; and by Dr. Haug, with a query, to Am. compactilis, Simpson. At any rate 

 it differs totally from Sowerby's Am. concavus in suture-line and ribbing, also in 

 having a straight or slightly convex inner margin, and an open umbilicus. 4 MM. 

 Chapuis and Dewalque 5 also figure under the name Am. concavus, Sowerby, a 

 species which appears very probably to belong to the genus Pseudolioceras. Its 



1 See p. 62 concerning an error in the drawing of the front view of the type. 



2 The figures of this species given by Dr. Wright ('Lias Amm.,' pi. lxiii, figs. 1 — 3, Harpoceras 

 elegans) not being correctly drawn are likely to be misleading. The specimen is now in the British 

 Museum (Natural History), numbered C 1859, and a comparison with the figure shows that the 

 umbilicus is drawn too small the lower part of the outer whorl too broad, the centre of the umbilicus 

 a trifle too high up, and the carina (in fig. 3 especially) too acute. 



3 ' Lias Ammonites,' p. 444 



4 See p. 86, Pseudolioceras co?npactile. 



5 " Fossiles de Luxembourg," ' Mem. Acad. Belgique,' Bruxelles, 1853, pi. viii, fig. 3. 



