8 



BRITISH FOSSILS. 



retaining the generic name Ceraurus. We had previously selected 

 this beautiful example from the collection of Mr. Williams, who 

 found it near Llandovery, and we have since again examined it. 

 It is much elongated and narrowed upon the cleavage of the rock, 

 but is identical with the present species, and is very interesting as 

 showing that the Lower Silurian form is somewhat intermediate, 

 as regards the tail, between the ordinary Dudley form and our 

 var. /3, for the lower prongs are but slightly distant, and have but a 

 tubercle, instead of a prominent mucro between them. 



Barrande's exquisite figures of the genus, fortunately now 

 before us, show the structure of all parts of the body completely. 

 He has figured the hypostome in several species ; we are fortunate in 

 here being able to add the under side of that organ, and the struc- 

 ture of the eye. 



British Localities and Geological Range. — Llandeilo Flags to 

 Aymestry Limestone. — In Llandeilo flags; Sholes Hook, and 

 Pelcombe Cross, Kobeston Wathen, and Llandowror, near Haver- 

 fordwest; Goleugoed, Llandovery, (Cambridge Museum). In Bala 

 limestone ; Rhiwlas and other localities, near Bala, North Wales ; 

 Chair of Kildare, Ireland. In Lower Silurian rocks, at Mullock, 

 Girvan, Ayrshire, (CoU. Sir K. I. M.) In Woolhope limestone ; 

 Nash Scar, Presteign, (Coll. Mr. Davis.) In Wenlock limestone ; 

 Haven, near Aymestry, (Coll. Eev. T. T. Lewis) ; Brand Lodge, Mal- 

 verns ; Dudley ; Dormington Wood, Woolhope. In Aymestry lime- 

 stone ; Downton Castle, Ludlow. 



Far. (3. — In Wenlock strata ; Nelson's Tower Wood, east of 

 Carmarthen. 



Foreign Distribution. — Gothland, in Upper Silurian (Hisinger) ; 

 ((Eland, Lower Silurian, Dalman?). 



Explanation of Plate II. 



Fig. 1, Specimen, perfect except the tail, from Haven, near Aymestry ; in the collec- 

 tion of the Kev. T. T. Lewis, of Bridstow, Ross. 



Fig. 1*. Head of same, dissected, showing the granulate glabella, a, and deeply pitted 

 cheeks, b, c. (the eye is raised too much.) 



Fig. 2. From Dudley, collection of J. Gray, Esq. A fine half coiled specimen, showing 

 the whole 1 1 rings, and the small tail. 



Fig. 3. Same locality and collection. Very young coiled specimen. 



Fig. 4. Same locality and collection ; showing the under side and incurved edge of the 

 tail, with the spines a little more apart. 



Fig. 5. Tail of young specimen, from Dudley ; collection of T. W. Fletcher, Esq. It 

 has the posterior spines approximate. 



Fig. 6. Same locality ; collection of J. Gray. 



