PSEUDOLIOCERAS COMPACT1LE. 85 



Pseudolioceras compactile (Simpson). Plate XX, figs. 3 — 6. 



1855. Ammonites compactilis, Simpson. Fossils Yorkshire Lias, p. 75, No. 119. 

 1874. Ammonites lythensis, Dumortier (non Young and Bird). Etudes pal. 



Bassin Rhone, iv, pi. xi. figs. 9, 10. 

 1876. Haepoceeas compactile, Blake. Yorkshire Lias (Cephalopoda), p. 308, 



pi. viii, fig. 6. 

 1884. — — Haug. Ammonites nouvelles ou peu counties, 



Bull. Soc. geol. France, 3 e serie, t. xii, 

 pi. xiv, figs. 1 a — c. 



1884. Ammonites compactilis, Simpson. Fossils Yorkshire Lias,2nd edit., p. 110. 



1885. Haepoceeas compactile, BZaug. Beitrage Monog. Harpoceras, Neues 



Jahrbuch fur Min., &c, Beil.-Bd. iii, 

 p. 623, pi. xi, fig. 15. 

 1885. Ammonites falcodiscus, Quenstedt. Ammon. Schwabischen Jura, pi. liv, 



figs. 23, 24, 24 bis, 25, and 48. 

 1887. Ammonites Wuettenbeegeei, Denckmann. Fauna Ob. -Lias Dornten, Abh. 



geol. Specialkarte Preussen 

 und Thuringischen Staaten, 

 Bd. viii, Heft 2, pi. i, figs. 1, 

 2 ; pi. iv, fig. 7. 



Discoidal, compressed, with a hollow carina ; whorls broad, subconvex, 

 sloping gradually towards the ventral area, ornamented with simple subfalciform 

 radii, which develop, on the outer lateral area only, into broad, wave-like, slightly 

 curved ribs. The inner area is slightly subconvex, and crossed by fine straight 

 strias. The ventral area is extremely narrow, being in fact almost occupied by the 

 carina, which is thus bordered by two very small depressions cutting it off from 

 the lateral area. The carina is prominent, and of the hollow type. The inner 

 margin is deep and upright, and its upper edge is raised just slightly above the 

 level of the whorl, thus creating a concave depression in the inner area. About 

 five-sixths of the inner whorl is occluded, so that the umbilicus is small and deep, 

 formed of small steps, and quite smooth. The aperture is acutely sagittate. 



This species has only recently been satisfactorily determined, although its 

 name has been in use for a number of years. Simpson described it in the year 

 1855 in the following terms : — " Much depressed, inner volutions nearly concealed, 

 outer whorl more than half the diameter ; radii waving, nearly obsolete ; obsoletely 

 striated ; keel rounded, entire ; aperture acutely triangular or ovate ; diameter an 

 inch and a half." With this description he gave no figure, so that to anyone 

 unacquainted with the Yorkshire fossils the chances of correctly determining the 

 species would be extremely small. Therefore this species cannot be said to have 

 had any real existence until, in 1876, Prof. Blake revived the name, and gave a 

 figure of the fossil. I believe that, fortunately, no question of priority arises, the 



