176 



BRITISH PALEOZOIC ASTEROZOA. 



channel was not recognised, however, until the figure had been drawn, and it is 

 not shown. The A is kept in position by the odontophor, which has wide flanges 

 fitting against outer flanges of the ambulacralia. The intimate connection and 

 close fitting of these components suggest that the odontophor played a very 

 important part in holding the mouth-frame together. 



Here and there accessory stiffening plates (Text-fig. 115) are exposed. I have 

 termed these "superambulacralia," after the plates of similar function in the recent 

 Astropecten. The madreporite is a long, roughly elliptical plate, situate near the 

 margin (Plate XIV, fig. 1). The madreporiform markings are faint. 



A 



m. 



o. 



Text-fio. 121. — Wash drawing of the apical view of the interradial month-region of Platanaster urdovicus, 

 A., ascending limit of the mouth-angle plate ; Am., ambulacra! ; O., odontophor. x 10. 



Measurements. — R : r : 

 Horizon and Locality. 

 Shropshire. 



43 mm. : 15 mm. Width of arm at the base is 17 mm. 

 -Upper Ordovician (Caradocian) of Cound, Madeley, 



Genus PALASTERISCUS, Stiirtz. 



1886. Palasterhcus, Stiirtz, Palaeontographica, vol. xxxii, p. 95. 



1890. „ Stiirtz, Palseontographica, vol. xxxvi, pp. 223-225. 



1893. ,, Stiirtz, Verhandl. Naturh. Ver. preuss. Rheinl., Jahrg. 50, pp. 44, 61. 



1900. ,, Gregory, Lankester's Treat. Zool., vol. iii, Echinodernia, p. 257. 



1914. ,, Schuchert, Fossilium Catalogus, Animalia, pt. 3, pp. 5, 8, 32. 



1915. „ Schuchert, Bull. 88, U.S. Nat. Mus., pp. 44, 199, 200, 252. 



Generic Characters. — No infero-marginalia. Madreporite oral. 



Stiirtz, as was his custom, tried to establish relationships of his genus with 

 recent Asteroidea. At first (1886) he thought that these were with Asterina and 

 Palmipes ( = Asteriscus, Miiller and Troschel), but later (1890) he decided that its 



