464 THE LIAS AMMONITES. 



sloped into a trenchant, slightly prominent carina without a keel, over which fine 

 striae pass j test moderately thick, striated with many fine, falciform depressions, 

 sometimes fasciated ; siphuncle lies immediately beneath the carina, which envelopes 

 it ; aperture elongate, sagittate, with projecting lateral lappets, and a long abdominal 

 spine ; suture-line tortuous. 



Dimensions. — Transverse diameter 115 millimetres; width of umbilicus 25 milli- 

 metres ; height of aperture 50 millimetres ; width of ditto, 24 millimetres. 



Description. — This beautiful Ammonite characterises the uppermost stratum of the 

 Liassic sands in Gloucestershire and Dorsetshire, where I have collected it in situ. In 

 Germany this same stratum with Lyioceras torulosum is classified with the Brown Jura 

 or Lower Oolite, but the English sections have induced me to place it with the 

 Ammonites of the sands. I have taken a specimen at Haresfield in a block of rock with its 

 impression on the Lower Oolite which rested immediately upon it, so high does it range. 



The shell is compressed, discoidal, and strongly carinated, but without a distinct 

 keel ; the volutions, six in number, are about two thirds involute, raised a little in the 

 middle, convex on the outer half, and slightly depressed on the inner. The whorls 

 are likewise concave at the inner margin, where they embrace the umbilicus, and curve 

 towards the siphonal area, where they form a trenchant carina without a distinct keel, 

 producing an acute bevelled edge over which striae pass from the right to the left side of 

 the shell, as shown in PI. LXXX, figs. 7 and 8. 



The surface of the shell is ornamented with innumerable fine striations, rather unequal 

 in size, biflexed in figure, and extending uninterruptedly from the umbilicus to the area. 

 The striae are sometimes fasciated at the inner margin from the clustering together 

 of so many striae into a limited space. In many shells this is wanting, but may be 

 noted in the two fine examples (PI. LXXX, figs. 4, 6). The aperture is compressed, 

 elongated, and sagittate. The sides have, when perfect, long, narrow, lateral lappets 

 and a projecting abdominal spine, all of which leave their impression on the mould of 

 the body-chamber, 



The suture-line is tortuous, and forms six lobes on each side. The siphonal lobe is 

 shorter and as wide as the principal lateral, and ornamented on each side with two 

 branches, of which the terminal one is bifid. The siphonal saddle is wide and divided 

 into two portions by a long accessory lobe ; the innermost is the widest and terminates 

 in two complex and one simple foliole, the outer portion is long and narrow and develops 

 several lateral folioles. The principal lateral lobe has a long, stout, straight stem, with three 

 digitations on each side and three terminal branches. The lateral saddle is very symmetrical, 

 and as large as the principal lateral lobe; it is divided into two parts by a short accessory lobe 

 at the base, and the sides and bottom terminate in a number of rounded leaves. The inner 

 lateral lobe is narrower and shorter than the principal lateral, and its sides and terminal 

 portion develops many pointed digitations. The outer auxiliary saddle is rather large, 

 developing a number of folioles; the first auxiliary lobe is a little smaller than the 



