} 
-ECHINOID FROM THE CRETACEOUS OF BRITISH COLOMBIA 
107 
Fig. 5. Plesiaster vancouverensis sp. nov. A, BMNH EE5076, adapical view of test showing tuberculation style, x1. B, BMNH EES083, latex cast of 
external mould showing apical disc and tuberculation style, x2. 
a partial peripetalous fasciole represents an apomorphy for the genus 
and the distinction is maintained here. The European species that 
have been assigned to this genus in the past, P. bucardium Goldfuss, 
P. coravium Schliiter, P. parvistella Schliiter, and P. minor Schliiter 
(e.g. Ernst 1972), differ significantly from the North African type, P. 
peini Coquand. The European species all have short petals, non- 
petaloid anterior ambulacra, and complete peripetalous and subanal 
fascioles. They are placed in the genus Diplodetus Schliiter 1900. 
The two North African species, P. peini and P. cotteaui have much 
longer petals and incomplete fascioles. 
The Canadian species comes close to ‘Micraster’ americanus 
Stephenson in form, but differs from that species in having a much 
more strongly petaloid anterior ambulacrum. In M. americanus the 
dores in the anterior ambulacrum are small and separated by a raised 
nterporal granule, whereas those pores in P. vancouverensis are 
“ater and widely separated from one another in each pair. 
“urthermore, the petals of P. vancouverensis are larger, more open 
and extend closer to the ambitus than they do in M. americanus. 
F. vancouverensis differs from the North African species of 
Plesiaster in having a well-developed peripetalous fasciole around 
{he posterior of the test. P peini and P. cotteaui both have very 
mpersistent fascioles that are really only present at the base of the 
detals and do not form a continuous band around the posterior. 
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Columbia. A, B, BMNH EES078 (internal mould), holotype: A, apical view; B, oral view. C,D, BMNH EES081 (internal mould), paratype: C, apical 
view; D, oral view. E, F, BMNH EE5S079 (internal mould), paratype: E, apical view; F, oral view. All x1. 
