﻿PYCNASTER ANGUSTATUS. 21 



and their ornamentation, as well as the presence of the peculiar pedicellariae, 

 and indeed the whole facies of this fossil, lend strong support to the presumption 

 that this species may ultimately need to be placed in a distinct genus, but I do 

 not feel warranted in taking that step on the basis of such scanty material. 



Genus— PYCNASTER, Sladen. 



Disk relatively small and pentagonal. Abactinal surface more or less convex, 

 and was probably somewhat inflated during life. Margin thick, and highest 

 in the region of the disk. Rays elongate, narrow, and robust. Marginal plates 

 forming a broad border to the disk, and united along the median abactinal line of 

 the ray throughout. The marginal plates are high and very robust, those of the 

 superior series being prominently convex abactinally in the median line of breadth 

 and height, which imparts a well-rounded character to the ray. The marginal 

 plates of both series are finely granulated, and probably bore no spines. Actinal 

 intermediate plates large, covered with uniform granules. Armature of the 

 adambulacral plates arranged in longitudinal series. Foraminate pedicellarias 

 with radiating channels may be present on the marginal plates. 



The fragmentary state of the fossils which I have referred to this type 

 unfortunately does not permit of a complete diagnosis of the genus being drawn 

 up. The characters above given appear, however, to me to be sufficient to 

 warrant the recognition of the possessors of them as the representatives of a 

 distinct genus. The small high disk, the massive convex marginal plates, 

 and the large actinal intermediate plates, together with the form of the rays, 

 produce a facies alone sufficient to stamp its individuality, irrespective of other 

 details of structure. 



1. Pycnastbb angustatus, Forbes, sp. PI. IX, figs. 1 a, lb. 



Goniaster (Astrogonium) angustatus, Forbes, 1848. Memoirs of the Geolo- 

 gical Survey of Great Britain, 

 vol. ii, p. 474. 

 — — — — ■ 1850. In Dixon's Geology and 



Fossils of the Tertiary and 

 Cretaceous Formations of 

 Sussex, London, 4to., p. 335, 

 pi. xxiii, fig. 10. 



