AEGOCERAS LAQUEOLUS. 315 



" In one specimen the foliaceous septa ai'e distinct ; they form a succession of sinuous 

 lobes, augmenting in breadth from the interior to the exterior of the whorl. In some 

 specimens the mode of petrifaction appears to have been curious : in one, for example, 

 an outer whorl is at one end filled by the grey gritty limestone of the surrounding rock ; 

 whilst at the other, by the section, it appears half occupied by the limestone and half by 

 white calcareous spar; and again, an inner whorl is entirely occupied by the spar. 

 Ballintoy: indurated shale of trap dike. — This specimen held to the light shows the 

 traces of obsolete ribs or striae over the front, apparently three between each pair. 

 Glenaven, Cairncastle, Tickmacrevan : calcareous or gritty grey limestone, same as 

 Ballintoy. Where the shell is perfect the front is quite smooth. In the inner whorls 

 the depth is equal to the width, and in the cast the ribs, on coming to the front, where 

 they appear slightly curved, vanish away without visibly passing over, though occasion- 

 ally there is a trace of such passage sufficient to become perceptible to the finger, or, 

 under a strong light, to the eye. As the whorls augment the breadth increases more in 

 proportion than the depth, and the ribs become comparatively less until at length they 

 have exactly the position of those of A. Jolmstoni. Ballygalley Head : there appear to 

 be two varieties of this species ; the ribs of one being more distant from each other than 

 those of the other, and its section rounder ; the form of the septa is the same. Island 

 Magee, Gobbin's Head : same rock, but with sparry fragments, resembling, therefore, 

 the Aghanloo bed, which contains the A. Sampsoni ; one specimen strongly exhibiting 

 the character of A. Jolmstoni. Another beautiful mode of petrifaction is exhibited by 

 one of the specimens. The inner whorls are entirely filled with white calcareous spar ; 

 but the outer whorl is empty in the centre, the circumference being lined with spar, for 

 about '1 of an inch, from which project towards the centre numerous acute crystals, 

 the spaces between their opposite points being unequal, according as the process of filling 

 up has more or less advanced." 



Affinities and Differences. — I have figured two examples of this Ammonite belonging 

 to the Museum of the Irish Geological Survey, and kindly lent by my old friend, Professor 

 Hull, E.R.S. The specimen (fig. 5) M^as General Portlock's type specimen. The 

 affinities between this species with Aeff. Belcheri, and both with Ae^. Jolmstoni, are so 

 numerous, and the diS'erences so few, that I am inclined to group them both along with 

 the latter form until better specimens are discovered for a comparison of the species. 



Aegoceuas LAQUEOLUS,^ SMoenbach. PI. XV, figs. 1, 2, 10 — 12 ; PI. XVI, figs. 1, 2. 

 Ammonites lasubolus, Schloenbach. Beitr. Pala., p. 152, pi. ssvi, fig. 1, 1865. 



1 On the explanation of PI. xv, figs. I and 2 are termed A. Liassicum, figs. 10 — 12, J., tortile ; on 

 PI. xvi, figs. 1 and 2, are termed A. Liassicum. See Synonyms, p. 316. 



