BRITISH FOSSILS. 



5 



Locality and Geological Position. — Llandeilo Flags, (lower 

 portion?) Glan-y-gors, three miles south-east of Llanerchymedd, 

 Anglesea, in nodules among black shale, containing also Graptolites 

 and Lingula. 



Affinities. — rediviva, the first described species of this genus, 

 differs from JE. mimhilis by a much broader glabella, and smaller 

 eyes which do not meet in the front ; nor is this latter remarkable 

 character known in the other Bohemian species. In other respects, 

 in the tail and six thoracic rings of the same general form, uE. redi- 

 viva is very like our species, the axis of the thorax being very wide 

 in front, while the corresponding pleurae are small ; it has also a 

 similar pair of glabella furrows. JS. pachycephala has large but 

 angular eyes, and only five thoracic segments ; the other species, 

 speciosa^ Corda, does not require comparison. 



The afiinity of the genus itself is pretty clearly with the Asaphoid 

 group, with which, especially with such forms as Nileus and Illsenus 

 it has many points in common. The form of the thorax rings and 

 the smooth almost lobeless glabella are indications of this ; and on 

 the under side of the head, the tranverse striated rostral portion 

 strikingly recalls the analogous part of Illsenus (see Decade II., 

 pi. 2. fig. 4), although the rostral shield is not separate. The 

 grooved pleurae, facetted for rolling up, and truncate at their ends, 

 are more like those of Asaphus ; and the tail^ with its abbreviated 

 axis and few obscure lateral ribs, reminds us of Ogygia Portlockii. 

 Its affinities seem, therefore, more evident with the Asaphoid group 

 than with Bronteus, to which in other respects the genus does not 

 seem very closely allied. But in the extraordinary development of 

 the eyes at the expense of the cheeks, it has no analogue that we 

 know of, except the Remopleurides, as figured in our plate 8 of this 

 Decade. With that group it appears to have no real affinity. 



The genus is only yet known in the Lower Silurian rocks. 



Explanation of Plate X. 

 Fig. 1. Perfect head of wiimSiVw. Portrane; natural size. 



Fig. 2. The same, magnified ; at a, the small prominences beneath the glabella furrows 

 are seen. 



Fig. 3. The same, side view ; at a, the posterior termination of the facial suture j b, the 



scarcely perceptible outer margin of the cheek- 

 Fig. 4. Front view, showing the large reticulated e\ es meeting in front. 



