62 FOSSIL ASTEROIDEA. 



were previously borne (see PI. XII, fig. 3 e). A small entrenclied pedicellaria may 

 be present on an occasional plate here and there. 



Dimensions. — The example figured on PI. XII, fig. 3 a, has a major radius of 

 about 30 mm., and a minor radius of about 28 mm. The length of the side is about 

 36 mm. The thickness of the margin is about 10 mm. In the specimen given on 

 PI. XV, fig. 4 a, the major radius measures 21 mm., and the minor radius 19 mm. 

 approximately. The length of the side is about 25 mm. 



Locality and Stratigra^yhical Position. — This species is a characteristic Upper 

 Chalk form. The majority of examples are from Kent and Sussex. A fine series 

 from Bi'omley is preserved in the British Museum. 



History. — This species was referred to by Dr. Mantell under the name of 

 Goniaster regularis. The specific name was, however, already preoccupied — at 

 least in literature — for an existing starfish ; and although the latter is not now 

 recognisable, no doubt can possibly exist that Mantell's fossil species is certainly 

 a different thing from the starfish to which Linck gave the name of Pentagonaster 

 regularis. 



Forbes was the first to describe the species under the name of Goniaster 

 {Goniodiscus) Hunteri, and his type-specimen, which is figured in Dixon's ' Geology 

 and Fossils of the Tertiary and Cretaceous Formations of Sussex,' pi. xxi, fig. 1 , 

 formed part of John Hunter's Collection, now preserved in the Museum of the 

 Royal College of Surgeons. The examples, illustrated in the present work are all 

 preserved in the British Museum. 



Variation. — There are at least two well-preserved examples in the collection of 

 the British Museum which I consider to be varieties of this species. They are 

 characterised by the presence of only four supero-marginal plates on each side of 

 the disk, exclusive of the odd terminal plates, as against six plates in typical 

 examples. Beyond this difference in number and the relatively greater length of 

 the supero-marginal plates in proportion to their breadth, I can indicate no 

 character worthy of being noted which would distinguish the examples in question 

 from the typical form of Mitraster Hunteri. The specimens under notice measure 

 35 mm. and 30 mm. in diameter (R -{- r) respectively. Both are from the Upper 

 Chalk, one from near Bromley, the other being only labelled " Kent." Figures 

 of the first-mentioned are given on PL IX, figs. 3 «■ — 3 e. 



