PCECILOMORPHUS CYCLOIDES. 117 



This small, and, on account of its narrow whorls, thin, compressed species 

 does not present so much variability in shape as Pcecil. cycloides. It does not 

 seem to attain a size greater than one inch in diameter, and in appearance is much 

 like a dwarf Hildoceras ; but it is effectually distinguished by the very different 

 position of its superior and inferior lateral lobes with regard to the rest of the 

 suture-line. From any variety of Poecil. cycloides it is separable by its thinness 

 and great evoluteness. It is much more likely to be passed over among the 

 young forms of Witchellia? which occur far more numerously in the same bed, 

 and which, when their test is absent, exhibit furrows along each side of a more or 

 less sunken carina. Our species may, however, be distinguished by possessing a 

 solid carina, sigmoidal ribs, and a more simple suture-line. 



The Sauzei-zone of Oborne, Dorset (p. 8), and the beds between the Lower 

 Ragstones and " Ironshot " of Dundry (Somerset) are the only localities where I 

 know this very scarce and interesting species to occur. 



Plate XXII, fig. 23, shows a side view of a nicely preserved specimen with 

 a complete mouth-border, exhibiting the short, perfect, lateral lappet; the back 

 view, showing the ventral lappet and the furrows on each side of the carina, is 

 given by fig. 24. Figs. 25, 26, 27, and 28 illustrate two more forms of this 

 species. The ventral furrows are, perhaps, scarcely conspicuous enough, 

 especially in fig. 28. Fig. 29 shows the suture-line of a specimen at its natural 

 size, while Plate A, fig. 33, exhibits the same enlarged. 



Pcecilomorphus cycloides (d'Orbigny). Plate XXII, figs. 1 — 22; Plate A, 



figs. 31, 32. 



1844. Ammonites cadomensis, d'Orbigny (non Defrance). Pal. Franc. Ceph 



Jurass., pi. cxxi, figs. 1 — 6 (non 

 pi. cxxix, figs. 4 — 6). 



1845. — cycloides, d'Orbigny. Pal. Franc. Ceph. Jurass., p. 370. 

 1856. — — Oppel. Jurafbruiation, p. 370. 



1881. Habpoceras cycloides, S. Buclcman. Inf. Ool. Ammonites ; Quart. Journ. 



Geol. Soc, vol. xxx vii, p. 604. 

 1885. Hildoceras cycloides, Haug. Beitrage Monog. Harpoceras ; Neues 



Jahrbuch f. Min., &c, Beil.-Bd. iii, 



p. 639. 



Discoidal to subglobose, carinate ; whorls subquadratc, their sides very slightly 



1 See p. 82. 



