226 
THE LIAS AMMONITES. 
mantle around tlie month-boi-dei- of the species possessing these fimbriated projections. 
A similar structure is likewise found in Lijt. hirciimin, from the Lijloceras Jurense zone. 
Fig. 123. — Lyloceras^ flmhriatum. Sow. Fig. 124. — Phylloceras lieteropliyllum. Sow. 
In Phylloceras the involute shell of this group is marked with true forward inclined 
lines of growth, indicating the presence of a ventral process at the abdominal side of the 
mouth-border, and this appears to have been the case in the only specimen with a fan- 
shaped body-chamber, Fliylloceras heterophyllmn (fig. 124), which I obtained from the 
Upper Lias at Whitby, of which I have given a figure on my Plate two thirds natural size. 
A remarkable form of mouth-border has been figured by Count Miinster under the 
name ScapJdtes refractus (fig. 125). In this species the abdominal or siphonal area forms a 
beak-shaped process, curved downwards towards the aperture, and the lateral processes 
rise into angular projections, producing a curious pentagonal-shaped oral aperture in 
this shell. 
Fig. 125. Fig. 126. Fig. 127. Fig. 128. 
Scaphiies refractus, Miinst. Lobites delphinocephalus, Hauer. Trachyceras Aon, Miinst. 
A still more remarkable mouth-border is seen in the curious example figured 
(fig. 12G) Lobites delphinocephalus, Von Hauer, in which the siphonal area becomes 
inflated and projects forward as in a Scaphite in a remarkable peak-shaped prominence ; 
Count Miinster, has figured a remarkable fossil, Trachyceras Aon (figs. 127, 128), in 
which the ornamentation of the shell indicates a sino-ular structure of the mouth-border. 
D 
^ Written Aegoceras in error on page 198. 
