A small and scarce form of chalk starfish, similar to the common Crateraster quinqueloba but distinguishable by its swollen arm tips.  This form was originally included within Pentagonaster obtusus, but was excluded when P. obtusus was redescribed as Nymphaster obtusus.  These starfish do not, therefore, belong within Nymphaster and await a proper designation.

1).  Aboral (upper) surface of a very well preserved individual (x2.3, White Chalk, Kent, BMNH (British Museum (Natural History) London) 40400.  Image © 2005 The Natural History Museum, by kind permission.

2).  Oral (under) surface of two associated individuals (x1.8, White Chalk, Kent, Taylor Collection, BMNH (British Museum (Natural History) London) 35481.  Image © 2005 The Natural History Museum, by kind permission.

3).  Detail of the above specimen, showing the swollen arm tips.  Image © 2005 The Natural History Museum, by kind permission.

4).  Detail of Fig 1, showing the madreporite.  Image © 2005 The Natural History Museum, by kind permission.