208 DEVONIAN FAUNA. 



2. Peotasteb? (Drepanaster) scabkosus, Whidbome. Plate XXIX, figs. 1 — 2 a. 



1896. Protaster scabrosus, Whidbome. Proc. Gt-ol. Assoc, vol. xiv, p. 377. 



Description. — Animal small, with long, narrow, regularly tapering arms. Disc 

 probably one-fourth or one-fifth the width of the expanded animal, subcircular, 

 covered on its dorsal surface with comparatively large squamiform overlapping 

 plates, which appear to be subquadrate in shape. Dorsal surface of arms covered 

 with similar, but smaller, squamiform plates. Ventral surface of arms with (1) a 

 double median row of ambulacral plates, excavated at their outer ends by moderately 

 large pores, and (2) a marginal row of elongate arching adambulacral plates, whose 

 proximal ends in part bound these pores, and each of which bears a group of two 

 or three spines. Buccal plates (ten ? paired) apparently rather large, giving, in 

 the cast, the appearance of a short-rayed star on the under side. 



Size. — A specimen with twisted arms measures 22 mm. One of the arms is 

 about 20 mm. long, so that the expanded animal probably measured about 37 mm. 

 across. 



Localities. — There is a good specimen from Croyde in the Barnstaple Athenaeum, 

 and another from Braunton Down in the Museum of Practical Geology. 



Remarks. — It is to be observed that the ambulacral plates in this species dis- 

 tinctly alternate. This appears to be consistent with Forbes's original definition 

 of the genus Protaster ; though, from Salter l having described them in P. Miltonii 

 as level (by way of exception), Hall and others seem to have come to regard this 

 as a generic character — Hall, however, questioning it, as in P. Forbesii, Hall, 3 they 

 slightly alternate. It appears to me, however, that for various other reasons, 

 P. scabrosus, together with P. Forbesii, with which it appears to be congeneric, 

 will have to be separated from the genus Protaster as defined by Forbes ; from the 

 shape of its adambulacral plates it might perhaps bear the name of Drepanaster. 3 



3. Protaster? (Dkepanaster) scabrosus, var. Plate XXVII, figs. 1 — 3; and 



Plate XXVIII, figs. 1—2 6. 



Description. — Animal small, five-rayed. Disc large, circular, covered with very 

 small plates. Rosette large, subpentagonal. Arms long, rather stout at the base, 

 regularly and rather rapidly tapering, and having on their under side a double alter- 



1 1857, Salter, * Ann. Alag. Nat. Hist.,' ser. 2, vol. xx, p. 330, pi. x,figs. i—ic (cf. p. 325, where 

 "Protaster, nov. gen.," is evidently a misprint). 



2 1867, Hall, ' Twentieth Report Eegents University, N.Y.,' p. 293, pi. ix, figs. 5, 6. 



3 Apeiruvov, a sickle. 



