4 BRITISH FOSSILS. 



Fig. 2**. Tail of ditto ; /, line marking the edge of the thin incurved portion of tail 

 [the lines that cover the tail in this figure are those of the upper surface] ; g, intermediate 

 furrow between 1st and 2nd. 



Fig. 3. Youngest specimen, with four body rings. Builth. 



Fig. 3*. The same magnified, to show the narrow caudal axis. 



Fig. 4. One rather more advanced, with seven body rings. Builth. 



Fig. 4*. The same, &c., magnified ; shows the tail a little turned aside. 



Fig. 5. Still older ; the eyes very forward ; eight rings. Builth. 



Fig. 5*. The same, magnified : shows the last thorax segment as yet imperfectly deve- 

 loped a. 



Fig. 6. Specimen of intermediate size, with short axis. Waterford. 



Fig. 7. Imperfect hypostome ; a a, concentric furrows. Waterford. 



Note on the Genus. 



The near affinity of Ogygia with Brontes has been perceived by Emmerich, who, in his 

 excellent paper, " On the Morphology and Classification of Trilobites," * placed it next to 

 that genus. The number of segments differs, 10 for Brontes, 8 for Ogygia; Brontes, too, 

 is sometimes very convex, while Ogygia is flat ; the shape of the glabella and caudal axis 

 differ materially, and there was no genus known which could fill up the interval between 

 the two genera. Both are expanded forms, characterized by large and strongly radiated 

 tails, and flattened glabellse, and by an obtuse, entire, furrowed hypostome. We are, 

 therefore, fortunate in being able to publish a species of Ogygia whose characters link the 

 genera much closer than before, and which, perhaps, might be regarded rather as a new 

 generic form, but that its habit is quite that of Ogygia. If we knew more species of the 

 genus, we would propose sub-genera for it, and might divide it into 



1. Glabella indistinctly lobed ; facial suture within the margin. O. Desmarestii, 

 Brongn. O. Edwardsii, Kouault. 



2. Glabella distinctly lobed ; facial suture within the margin. O. dilatata, Dalm. 



3. Glabella narrow ; facial suture on the margin. O. Buchii, Brongn. O. Guettardi, 

 Brongn. 



4. Glabella broad ; facial suture marginal. O. Portlockii. 



There are three or four undescribed British species of Ogygia, but at present we know 

 them only by fragments. 



J. W. SALTER. 

 June, 1849. 



* Leonhard and Bronn's " N. Jahrbuch," 1845, translated in Taylor's " Scientific 

 Memoirs," vol. iv. 



