144 BRITISH PALAEOZOIC ASTEROZOA. 



the radialia. The adradialia of the second row have pronounced stellate bases and 

 thin paxilla-shafts. A third row of very small adradialia maybe seen at the bases 

 of the arms. It is obvious that when the animal was alive, and the apical surface 

 consequently swollen, the ossicles formed a slightly open network through which 

 papulae could be protruded. The apical ossicles of V. grayse seem to form a closer 

 covering. The odontophor is visible on the apical surface. 



The infero-marginalia form a close overlapping border, each with a distinct 

 paxilla-shaft sticking out edgeways. Below the infero-marginalia the ridges of 

 the adambulacralia are readily discernible. There are about sixteen adambulacralia 

 to the first thirteen infero-marginalia. In the distal portion of the arm there are 

 suggestions that the adambulacralia and infero-marginalia are equal in number. 



The distal apical plates, as in U. grayse, are not strongly paxilliform and are 

 more closely fitting. 



The specimen from the Manchester Museum shows adambulacral spines 1*2 mm. 

 long. 



Measurements. — Ludlow specimen. R : r : : 14 mm.: 1 5 mm. 



Width of arm at base is 1*5 mm. 

 Manchester „ R : r : : 20 mm. : 1'9 mm. 



Width of arm at base is 2 mm. 



Horizon and Locality. — The Leintwardine (Lower Ludlow) beds of Herefordshire. 



3. Urasterella gutterfordensis, n. sp. Plate X, figs. 2, 3. 



Material. — Five moulds are known, four in counterpart. They were found at 

 Gutterford Burn, and are in the Collection of the Royal Scottish Museum 

 registered as 5, 29; 85,99; 67, 93; 14, 122; 70. The moulds give excellent 

 casts. Specimen 93 and its counterpart are taken as the holotype of the variety. 



Specific Characters. — The adambulacral ridges and the ambulacralia are as in 

 U. thraivensis, but there is the small plate additional to the centrale which is 

 characteristic of U. ruthveni. Mouth-angle plates small. 



Apical Surface (Plate X, fig. 2). — The best casts of the apical surface are given 

 by mould 93. The disc shows a centrale together with an extra plate as in 

 U. ruthveni, var. leintwardinensis. Surrounding these are six prominent plates 

 which are doubtless the five primary radialia and the single primary interradial. 

 A madreporite has not been recognised, probably because of the small size of the 

 specimen. Unfortunately, the exact arrangement of the other apical plates is 

 very difficult to determine, and I do not feel justified in giving an exact drawing. 

 They seem to me, however, to conform to the Urast&rella-jAan already described. 

 Prominent paxilla-shafts from the apical plates are seen both in this specimen and 

 in casts from 70. These latter casts also show thin overlapping infero-marginalia. 

 An odontophor can be seen in each of the interradial angles. 



