22 INFERIOR OOLITE AMMONITES. 



whether this character may be constant and peculiar to this class. As at present 

 constituted, this genus is one of the most important of the Hildoceratinge in the 

 Inferior Oolite. Of the type of this genus, Lioceras opalinum, Dr. Wright has 

 already given excellent figures and an exhaustive description ; l he claims it and 

 its zone as belonging to the Upper Lias, although he admits on page 464 that the 

 Germans hold different views. I have referred to this subject before (see the 

 Introduction) and stated the information and opinions I could obtain. There is 

 little doubt that in Gloucestershire the Opalinum-zone is more allied to the Upper 

 Lias, whilst in Dorset the sequence of strata is not sufficiently shown. We 

 must, however, look at general characters, and not at the peculiarity of a 

 particular district like Gloucestershire, when settling the question. 



Special Distinctive Characteristics. — These may be shortly stated as, when young, 

 evolute; in middle age, involute; adult becoming less involute proportionally; 

 inner margin concave ; differing especially from Ludwigia in absence of ribs on the 

 inner area and in having the siphonal saddle divided by a good-sized accessory 

 lobe, leaving the interior portion deeper than the exterior ; the lateral saddle also 

 divided by an accessory lobe, the inferior lateral lobe nearly as long as the 

 superior lateral, the first auxiliary lobe nearly as large as the inferior lateral ; all 

 these lobes touching those preceding them, and one suture line seeming to overlap 

 another. Suture line generally much incised. Four auxiliary lobes. 



Liocekas bradfobdense, 8. Buckm. Plate IV, figs. 5 — 8 ; Plate V. 



1881 Harpoceras Murchisonje, var. bradfordiense, S. Buchmnn. Quart. Journ. 



Geol. Soc, p. 604.. 

 1858 Ammonites Murchison^: acutus, Quenstedt. Der Jura, pi. 46, fig. 4 only, 



not 5. 



Shell discoidal, compressed, subcarinated, whorls compressed, very little 

 convex, ornamented with a number of small, plain, curved, but not prominent 

 costaB, sometimes bifurcated. Body-chamber smooth, with outer margin almost 

 rounded in adult specimens, and about half a whorl in length. Inner margin con- 

 cave. Inclusion quite three quarters of a whorl in half-grown specimens, less in 

 very young forms, and decreasing to half a whorl in full-grown ones. Aperture from 

 sagittate to suboblong. Mouth-border plain, produced on lateral and ventral areas, 

 rounded on the first and pointed on the second. Umbilicus always showing 

 portions of each of the inner whorls, like so many small steps. The suture line of 



1 ' The Lias Ammonites,' Wright, Palseont. Soc, vol. xxxviii, 1884, Plate LXXX, figs. 6 — 8, 

 pp. 463—466. 



