154 INFERIOR OOLITE AMMONITES. 



servation is too poor to admit of thorough identification. They exhibit a some- 

 what smaller umbilicus. 



Plate XXVI, fig. 3, represents the side view of a poorly-preserved specimen, to 

 show the general proportions. Fig. 4 shows a fragment somewhat better pre- 

 served ; while fig. 5 illustrates a sectional view of the same. 



Haugia occidentalis (Haug). PL XXVII, figs. 1, 2. 



1884. Hammatoceras occidentale, Haug. Nouvelles Amm. Lias superieur ; 



Bull. Soc. Greol. France, 3e serie, 

 t. xii, pi. XV, fig. 3. 



1885. Haepoceeas occidentale, Haug. Beitr. Monogr. Harpoceras ; Neues 



Jahrbuch fiir Mineralogie, &c., 

 Beil.-Bd. iii, p. 617. 



Discoidal, compressed, with a large hollow-carina. Whorls ornamented with 

 inconspicuous subsigmoidal ribs, which soon disappear, leaving the test quite 

 smooth. Ventral area not defined — the two sides of the whorl sloping gradually 

 towards a strong hollow-carina. Inner margin very distinct, flat, little sloped. 

 Inclusion about one-half. 



From all the preceding species of this genus this one is distinguished by the 

 absence of tubercles on the inner margin. It shares this character with Haugia 

 Eseri. I was at first inclined to consider these two species synonymous ; but, at 

 my request. Dr. Haug very kindly wrote to me concerning the difi"erences which 

 he had observed between them. I extract the following from his letter : 

 " H. Eseri .• — Ombilic limite par une surface perpendiculaire aux flancs de la 

 coquille (' steile Nahtflache '). Cotes peu flexeuses, assez grossieres et non 

 fasciculees, persistant j usque dans une age assez avance. H. occidentalis : — Ombilic 

 limite par une surface oblique par rapport aux flancs de la coquille (' geneigte 

 Nahtflache mit stumpfe Nabelkante '). Cotes flexeuses, peu saillantes, fasci- 

 culees, disparaissant entierement a une diametre de 1 decimetre^ environ." 



Unfortunately my specimens do not seem to altogether bear out my friend's 

 remarks ; and, apparently, these characters do not hold good in all cases. The 

 inner margin of H. Eseri is sometimes as oblique as in H. occidentalis ; the ribs 

 are not always fascicled in H. occidentalis, — on the contrary they are fascicled in a 

 variety of E. Eseri, Plate XXV, fig. 7, and incline to that way in other specimens ; 

 the ribs, also, sometimes die out in H. Eseri at a very early age, and are 

 sometimes stronger in H. occidentalis than in JI. Eseri. The chief difierences, to 



^ About four inches. 



