2 



BRITISH FOSSILS. 



plates, each bearing a crest at its anterior border indented by the 

 sockets of eight or more rather short cylindrical spines, which have 

 rugose surfaces. It is these crested marginal plates with their rows 

 of spines which give the under surface so much of the aspect of an 

 Astropecten. 



Dimensions of the largest Specimens. 



Inches. 



Diameter from apex of one ray to that of the one most distant . . . If^ 



Breadth of disk Of^ 



Breadth of a ray at origin ' • 0-^ 



Length of a ray from angle of junction 0^ 



Breadth of largest inferior marginal plate Of^ 



Length of marginal spine, rather more than 0^^ 



Locality and Geological Position. — This remarkable star-fish was 

 discovered by Mr. John Gavey, civil engineer, of Chipping Campden, 

 in the Lias of Mickleton Tunnel, Gloucestershire. Several specimens 

 occurred, and some fine examples, presented by that gentleman, are 

 displayed in the cabinets of the Museum of Practical Geology. 



Description of the Plate. 



Fig. 1 . Large specimen ; ventral surface displayed. 

 Figs. 2 and 3. Dorsal surfaces of two smaller examples. 



Fig. 4. Dorsal surface of a ray and part of disk, showing the keel-plates and their 

 arrangement. 



Fig. 5. Ventral surface of a ray and part of disk showing the ambulacra and angle- 

 plates. 



Fig. 6. Ambulacral plates and spiniferous plates bordering the ambulacra. 



Fig. 7. Margin plates. 



Fig. 8. Madreporiform plate. 



Fig. 9. A spine. 



Figs. 4 to 9 are highly magnified. 



Edward Forbes. 



June, 1850. 



