METOPASTER PARKINSONI. 35 
their surface is traversed by four or five ridges running parallel to the ambulacral 
furrow, with punctures upon which the spinelets composing the armature were 
articulated. There were four or five spinelets in each lineal series. The spinelets 
are short, their length being about equal to the length of the plate, stumpy, com- 
pressed, slightly tapering and rounded at the extremity ; and all appear to have 
been uniform. 
The actinal intermediate plates are rather large for the genus ; those adjacent to 
the adambulacral plates are pentagonal in form, but elsewhere they are subhexagonal, 
or perhaps more correctly polygonal. The plates are very large on the inner 
portion of the area, but diminish greatly in size at the outer margin of the disk 
adjacent to the marginal plates. The surface of the intermediate plates is entirely 
covered with small, equidistant punctations, upon which a uniform close granulation 
was previously attached. Remains of this granulation are still occasionally to be 
seen im sitw on plates here and there in the example under notice. Entrenched 
pedicellarize similar to those above described on the plates of the abactinal surface 
occur on a number of the plates in the series adjacent to the adambulacral plates, 
but the organ does not appear to diverge, or only very rarely, from the normal 
form of a central foramen and two lateral trenches. 
Dimensions.—In the specimen figured on Pl. X, fig. 2a, the major radius is 
38 mm., and the minor radius 30 mm. Other examples have the following 
approximate measurements: R=35 mm., r=27 mm.; R=43 mm., r=34 mm. 
The diameter of the disk (R+r) in well-grown tests ranges, therefore, from 
60mm. to 80mm. The thickness of the margin is about 11:75 mm. 
Locality and Stratigraphical Position.—All the examples figured in this 
Monograph were obtained from the Upper Chalk, near Bromley. The species is 
a characteristic Upper Chalk fossil in the south of England, and has been found 
in beds of that age at Brighton, Charlton, Gravesend, Kent, and other localities. 
It is stated by Forbes to occur in the Lower Chalk of Sussex, but I have not seen 
any examples from that horizon. 
History.—A fossil starfish which has been generally considered to be this 
Species was figured by Parkinson in his ‘ Organic Remains of a Former World,’ 
vol. iii, pl. i, fig. 3, but it was referred by that author to the Pentagonaster 
regularis of Linck. The last named has, however, been supposed to be a recent 
species, but the type has unfortunately been lost, and the form has not subse- 
quently been recognised definitely. Apart from this the fossil starfishes now 
under notice are certainly distinct from the form indicated by Linck’s figure, and 
this view was taken by Forbes, who named the species after Parkinson in his 
memoir ‘On the Asteriade found fossil in British Strata,’ and figures of the 
