2 



BRITISH FOSSILS. 



impressions in the neighbourhood of the ambulacral sulcus ; the ends 

 of the ossicula which go to form the sulcus are slightly denticulated. 

 The curvation of the ossicula has reference to the disposition of the 

 suckers, which in this genus are arranged in four series down each 

 avenue. The perforations are slightly ovate in this species. 



/ Dimensions. 



Inches. 



Breadth of disk 1 3^ 



Maximum breadth of a ray Oj| 



Maximum breadth of an ambulacrum 



Length of a ray from angle of junction with the body . . , , S^'^ 



Length of an ambulacrum from its origin at the mouth ... 4 



Affinities. — This species, as I have already indicated, approaches 

 more nearly to the existing Uraster ruhens and its allies than to any 

 described secondary or palaeozoic fossil. The Asterias lumbricalis and 

 the Asterias lanceolata of Goldfuss, both from the Jurassic beds in 

 Germany, have been referred by me to the genus Uraster* but they 

 are imperfect forms at best, and possibly, when found in more com- 

 plete condition, may prove to belong to other generic types. Not so 

 with the star -fish now described; there can be no mistake about its 

 generic position and affinities, as the most essential part of its osseous 

 framework, the ambulacral skeleton, is perfectly preserved. 



Locality and Geological Position. — The only specimen hitherto 

 found of this singular and beautiful fossil occurred in the Lias beds 

 laid open during the excavation of Mickleton Tunnel, in Gloucester- 

 shire. It was discovered by Mr. G. E. Gavey, civil engineer, of 

 Chipping Campden, Gloucestershire, who most liberally communicated 

 it for description and delineation to the Geological Survey. It lies on 

 the surface of a sandstone associated with fragments of Pentacrinites, 

 small Ammonites, Aviculse, and small univalves. 



Description of the Plate. 

 Fig. 1. The fossil, natural size. 



Fig. 2. Plan of the ambulacral plates and their spiny borders. 



Fig. 3. Diagram of the same parts in the living Uraster ruhens, introduced for comparison. 



Edward Forbes. 



June, 1850. 



* See "Table of Fossil Asteriadse" in vol. ii. pt. 2, p. 481, of the " Memoirs of the 

 Geological Survey of Great Britain." 



