140 BRITISH PALEOZOIC ASTEROZOA. 



2. Urasterella ruthveni (Forbes). Plate IX, fig. 5; Plate X, figs. 4 — G; Text- 

 figs. 90, 91. 



1848. Uraster ruthveni, Forbes, Mem. Geol. Surv. Gt. Brit,, vol. ii, pt. 2, p. 436. 



1849. ,, „ Forbes, Brit, Organic Remains, Mem. Geol. Surv., dec. i, p. 1, pi. i, fig. 1. 

 1851. Urasterella ruthveni, McCoy, Brit. Palaeoz. Foss., p. 59. 



1854. Urasfer ruthveni, Murchison, Siluria, fig. 39 — 3. 



1857. Palseaster ruthveni, Salter, Ann. Mag. Nat. Hist., ser. 2, vol. xx, p. 326. 



1862. „ ,, Wright, Mon. Brit. Foss. Echinoderm., Oolitic, vol. ii, pt. 1 (Palceontogr. 



Soc. for 1861), p. 25. 



1914. Urasterella ruthveni, Schuchert, Fossilium Catalogus, Animalia, pt. 3, pp. 28, 44, 45. 



1915. „ „ Schuchert, Bull. 88, U.S. Nat. Mus., pp. 174, 175, 187. 



Material. — Moulds of five specimens are known, all in the Sedgwick Museum, 

 Cambridge. Specimens a/920, a/921, n/510 are from the Bannisdale Slates, High 



Text-fig. 90. — Wash drawing of a portion of the apical surface of Urasterella ruthveni. Ad., adanibu- 

 lacralia; I.M., infero-marginals ; X, adradials. x 6. 



Thorns, Underbarrow. A cast from a/920 is figured by Forbes, and this mould is 

 taken as the holotype of the species. Upon the same slab as a/921 are two moulds 

 of Palasterina priw..xva, Forbes. Bl and B2 are from the Bannisdale Slates, 

 N. End of Benson Knot. Bl is a large specimen. B2 shows a portion of one arm 

 in side view. 



Specific Characters. — Ridge on adambulacralia set on distal edge of oral surface. 

 Ambulacralia long and narrow. 



Apical Surface (Plate IX, fig. 5 ; Text-fig. 90). — Unfortunately this surface is 

 not well shown, for no views can be obtained of the disc, and the arrangement of 

 the ossicles on the arm can only be made out very imperfectly. The text-figure 

 is drawn from a cast of the side view of the arm (B2). Upon the left side may be 

 seen some of the adambulacralia. Adjoining these are long overlapping infero- 

 marginalia of the usual Urasterellid paxillar form. Three rows of rather 

 irregularly scattered adradialia are next seen, while indications of another row 

 of similar ossicles are suggested. 



Oral Surface (Plate X, figs. 4— G; Text-fig. 91).— Except the fragment of 



