544 F. A. Bather— Studies in Edrioasteroidea. 



of Wattignies with Fhacops granulatus, Orthotefes crenistria, and 

 Clisiophyllum Oinaliusi, while the shales of Colleret and of Cousobre 

 below the " Psammites " have less thickness than the Famennian 

 shales elsewhere. In either case the " Psammites du Condroz " 

 must be taken as the uppermost member of the true Upper 

 Devonian, the succeeding limestones or shales being regarded as 

 beds of passage to the Carboniferous. The known forms most 

 nearly allied to Diiwcystis have not as yet been found above the 

 Ordovician. 



The Material. 



The seven specimens preserved in the British Museum are 

 registered E 7,581 to E 7,687, and may here be termed for short 

 1, 2, 3, etc., respectively. Of these 2 is selected as holotype, while 

 1 and 3-7 constitute the paratypes. 



All are internal casts ; but 3 and 7 had small portions of matrix 

 adherent to the under side, and these, being broken away, show 

 parts of the impression. 



In outline, as seen from above, the fossils are roughly elliptical, 

 but the orientation of the ellipse varies. A line drawn through 

 anus and actinal pole, and called the antero-posterior axis, almost 

 coincides with the long diameter of the ellipse in 1, 2, and 6 ; 

 in 3 the long diameter is shifted in the direction of the clock-hand 

 about 25° ; in 4 about 35° ; in 5 about 20° ; while in 7 the shift 

 is contrar}'' to the clock-hand about 75°. The measurements of the 

 diameters of the ellipse, in millimetres, are : — 



12 3 4 5 



43 38-5 35 32-5 30 



38-5 31 26-5 27-5 22 



Distance of actinal pole from posterior margin, in millimetres : — 

 1 2 3 4 5 6 7 



19-5 16 12-5 12 12 16 14 



These measurements show that the present shape of the specimens 

 is probably due to contortion after death, whether before or after 

 the consolidation of the matrix. But they further suggest that the 

 tendency was for elongation to take place in an antero-posterior 

 direction, and that in life as in death the actinal centre lay posterior 

 to the geometric centre. To confirm these suggestions there is 

 needed a larger series of specimens, and information concerning 

 their relations to the rock-masses in the field. 



Description of the Species on the Evidence of the Seven 



Specimens. 



One may compare the fossil in a rough way to a Tara-o'-Sbanter 

 cap or a Breton beret. 



The periphery was approximately circular, varying in diameter 

 from 41 mm. (1) to 22 mm, (7). 



From the periphery, the test curved gently over to the upper 

 surface, and rolled gently inwards on the under surface towards 



