224 BRITISH PALEOZOIC ASTEROZOA. 



Material — There are many specimens in various museums, nearly all impressions 

 in sandstone. Individuals are often crowded together on the same slab, suggesting 

 that, like many Ophiuroidea, the form occurred in swarms. The most extensive 

 collection is in the Sedgwick Museum, Cambridge, where there are twelve slabs, 

 with another slab which contains two impressions associated with Urasterella 

 ruthveni (see p. 140). Six of the slabs are stated to be from the Bannisdale Slates, 

 High Thorns, Underbarrow, and are registered as a/517. A note is attached to 

 the label that Forbes' original figures were based on this material. I have 

 identified one of the impressions (slab d) as giving the cast from which Forbes' 

 fig. 2 a was drawn, but I cannot recognise the original of fig. 2 b. The 

 specimen on slab <l is therefore hereby selected as the holotype of the species. 

 It is figured here, PI. XV, fig. 5. Four of the slabs (/, a, h, k) are labelled 

 Bannisdale Slates, nr. Kendal, and a note is attached that these were in a 

 Kirkby Lonsdale drawer unlabelled. The other two slabs are from the Bannisdale 

 Slates, High Thorns (no. 146*), and from Bannisdale Slates (?), Underbarrow 

 (no. 48), respectively. The British Museum (Nat. Hist.) has specimens registered 

 as E. 01, E. 4990 — 4993, all from Underbarrow. Specimens in the Museum 

 of Practical Geology, Jermyn St., are registered as 25349, 25350 and 25375. 

 The locality of the first is near Kendal, the other two are from Underbarrow. 

 The following specimens are in the Kendal Museum : no. 9 from the " Asterias 

 bed," Bannisdale Slates, Underbarrow ; nos. 7, 34, from the Bannisdale Slates, 

 High Thorns, Underbarrow. It seems clear that all the specimens are from the 

 same horizon and locality (see also p. 142). 



Specific Characters. — See p. 220. 



Oral Surface (PI. XV, fig. 7 ; Text-figs. 101, 1(32).— The adambulacralia are very 

 prominent indeed, and it is their shape and disposition which give the arm its dis- 

 tinctive appearance. They margin the arm, and the largest lie about the base of the 

 free portion of the arm, with the result that it has a distinctly petaloid appearance. 



Each adambulacral has a characteristic shape. It only meets its neighbours 

 along a comparatively slender articulation (Text-fig. 162). The surface above the 

 line of contact is much swollen. The nose, which is, as usual, on the proximal 

 portion of the ossicle, is continued into a ridge, which at first starts backwards, 

 and then runs along the middle of the ossicle. The ridge possesses pustular elevations 

 which carried long spines. Text-fig. 160, p. 223, gives a view of the ossicle of the 

 groove as seen from within (corresponding to the aspects figured Text-figs. 124, 

 125, pp. 183, 184). The adambulacralia look as if they were tipped away from the 

 mouth. This is due to slight distortion in the rubber cast from which the drawing 

 was made. Really they tip, as is usual, towards the mouth. The groove is deep, 

 and the adambulacralia form a steep wall just as in Urasterella (see p. 133). The 

 ambulacralia have the same general character as those of Schuchertia (Text-fig. 124, 

 p. 183). The median ridge as figured appears to be thicker and more rounded than 



