228 BRITISH PALEOZOIC ASTEROZOA. 



mouth. The first ambulacralia are somewhat long and touch only at their distal 

 ends. Each of the succeeding ossicles has a high median ridge (for the attachment 

 of the dorsal transverse muscle) and a lateral swelling. The line of junction of 

 successive ossicles is very close, and it appears as if the dorsal longitudinal muscles 

 were of small importance. 



An excellent apical view of the mouth-frame (Text-fig. 164) was obtained by 

 dissolving an embedded calcite specimen and taking casts as the process proceeded. 

 The arrangement of the various exposed parts is exactly as in Text-fig. 133, p. 191, 

 except that (a) the first ambulacralia do not dip so steeply, and (b) the basal portion 

 of the mouth-angle plate does not project so far into the mouth-cavity, (r) the 

 interradial faces of the apophyses show depressions for the adductor muscles, but 

 the adradial faces are smooth, suggesting that abductor muscles were absent 

 (see p. 192). 



Measurements. — The species varies in size between the following limits : largest 

 specimen on slab a, Sedgwick Museum, R : r : : 18 mm. : 5 mm. ; smallest specimen 

 on slab a, Sedgwick Museum, R : r : : 8 mm. : 3 mm. 



Horizon and Locality. — Upper Silurian (Ludlow) ; Westmoreland. 



2. Palasterina antiqua (Hisinger). Plate IV, fig. 6; Plate XV, fig. 9 ; Plate XVI, 



figs. 1, 2; Text-figs. 165—170. 



1837. Asterias antiqua, Hisinger, Lethea Suecica, p. 89, pi. xxvi, fig. 6. 



1857. Palasterina prinueviis, Salter, Ann. Mag. Nat. Hist. [2], vol. xx, p. 327, pi. ix, figs. 2 a — c. 



1862. „ „ Wright, Mon. Brit. Foss. Echin., Oolitic, vol. ii, pt. 1 (Palseontogr. Soc. 



for 1861), p. 26, fig. 16 a. 

 1899. Lindstromaster antiqua, Gregory, Geol. Mag. [4], vol. vi, pp. 343, 347, pi. xvi, figs. 1 a, lb. 

 1899. Palasterina bonneyi, Gregory, loc. cit. [4], vol. vi, pp. 349, 350, pi. xvi, figs. 2 a, b; text- 

 figs. 1—3. 

 1910. Lindstromaster antiqua, Schondorf, Jahrb. Nassauisch. Ver. Naturk., Wiesbaden, vol. lxiii, 



p. 225. 

 1910. Palasterina. bonneyi, Schondorf, loc. cit., vol. lxiii, pp. 223, 250. 

 1914. Lindstromaster antiquus, Schuchert, Fossilium Catalogus, Animalia, pt. 3, p. 23. 



1914. Palasterina bonneyi, Schuchert, loc. cit., Animalia, pt. 3, p. 31. 



1915. Lindstromaster antiquus, Schuchert, Bull. 88, U.S. Nat. Mus., pp. 149, 153. 



1915. Palasterina bonneyi, Schuchert, loc. cit., pp. 15 , 152, 153. 



1916. „ primieva, Spencer, this Monograph, pi. iv, fig. 6. 



Material. — I have placed in this species five specimens showing the oral 

 surface, two being from the same horizon : 



(1) The type of Lindstromaster antiquus, in the Angelin Collection of the 

 Mineralogical Museum, Copenhagen (no. 306), from the Ludlow of Gotland. 



(2) A new specimen from the Wenlock of Dudley, in Sir Charles Holcroft's 

 collection at the museum of the University of Birmingham (no. 1). 



