PROTASTER. 207 



P. Sedgwickii, Forbes, is the type of the true genus Protaster, from which the 

 superfluities will have to be removed. 



1. PROTASTER GRANIFBR, Whidbome, sp. Plate XXVI, figs. 5, 5 a, 6, 6 a. 



189G. EUGASTEB, GEANIFEB, Whidborne. Proc. Geol. Assoc., vol. xiv, p. 377. 



Description. Animal with a moderately large pentagonal disc, and rather long 

 arms, which are slightly fusiform at first, and then taper very slowly to a 

 distant extremity. Upper surface of disc marked by a large impressed stellate 

 corona, which is bounded by elevated sides, and is about half the width of the disc 

 in diameter. Upper and lower surface of disc and upper surface of arms covered 

 with an integument composed of minute convex scales, irregularly scattered 

 among still more numerous and minute granules. Mouth apparently small and 

 central. Oral or buccal plates apparently large, deep, and elongate. Upper 

 surface of arms having (1) two central alternating rows of transverse sub- 

 hexagonal plates, divided transversely by a linear groove, and (2) an alternating 

 lateral row of slightly convex squamose or imbricating plates, at the lower 

 margins of. each of which are situated one or more short, broad, ovate, slightly 

 curved spines. Under surface of arms with two alternating rows of narrow 

 ambulacral plates, excavated on their outer margins by pores, which are outwardly 

 enclosed by a row of obliquely protruding adambulacral plates, at the outer or 

 lower extremities of which the spines are situated. 



Size. A nearly perfect, but perhaps slightly elongated, arm measures 50 mm. 

 The size of the expanded animal was therefore probably about 90 mm. 



Localities. In the Museum of Practical Geology is a very fine specimen 

 (seen as casts of the upper and lower surfaces) from " the Pilton Beds of North 

 Devon." 



Remarks. Casts taken from the under surface of this specimen and from the 

 under surface of specimens of Protaster Sedgwickii, Forbes, 1 in the same Museum 

 appear accurately to agree in all points of the arrangement of the arms and plates. 

 The arrangement of the buccal plates appears also to be similar. Hence, as 

 P. Sedgwickii is the type of the genus, it appears that this is a species of 

 Protaster, in spite of the disc having a pentagonal form more in the shape of that 

 of the genus Eugaster, Hall. 2 



From P. Sedgwickii it differs in the large size of the corona and many other 

 minor particulars. 



1 1849, Forbes, ' Geol. Surv.,' Decade 1, p. i, pi. iv, figs. 14. 



2 18 67, Hall, ' Twentieth Eeport Eegents University, N. Y./ p. 290. 



