1907-8.] NOTES ON THE OPHIURIAN GENUS, PROTASTER 363 
NOTES ON THE OPHIURIAN GENUS, PROTASTER, WITH 
DESCRIPTION: OF \A°NEW “SPECIES. 
By WILLIAM ARTHUR PARKS, PH.D., 
ASSOCIATE PROFESSOR OF GEOLOGY, UNIVERSITY OF TORONTO. 
MANY diverse Palaeozoic Brittle-stars have been ascribed to this 
genus, and, although a comparatively recent revision is available, the 
classification can not yet be said to be satisfactory. The reason for this 
is to be found in the poor state of preservation of most examples and 
the consequent lack of knowledge of the details essential to a rational 
classification. It is believed that some additional light is thrown on the 
structure of these forms by the examination of the species about to be 
described. It is thought advisable therefore to preface the description 
proper by a short account of the development of our knowledge of the 
genus. 
The genus Protaster was erected by Professor Forbes for the recep- 
tion of a species (P. sedgwicki) from the Ludlow formation of Great 
Britain. The description, which was not very detailed, appeared in 
Decade i, British Organic Remains, Memoirs of the Geological Survey 
of Great Britain, 1849. The type specimen possessed a circular disc 
covered with squamiform plates, and five arms “formed of alternating 
ossicula.” Genital openings are said to occur in the angles of junction 
of the arms beneath. The next reference to Protaster is in the Annals 
and Magazine of Natural History for November, 1857. Two new species, 
P. mtltont and P. leptosoma, are described by Mr. J. W. Salter. The 
genus is more thoroughly defined, but, unfortunately for future workers, 
it is made to include forms with the ossicles opposite as well as those in 
which the arrangement of these elements is alternating. In this article 
Mr. Salter ascribes to this genus a form, P. salterz, described in the 
Quarterly Journal of the Geological Society for 1845, as Ophiura saltert 
by Sowerby. The genus 7e@nzaster was established by Billings in 1858, 
with two species, 7. spzmosus and 7. cylindricus from the Trenton of 
Ontario. As this genus has been thought to be identical with Protaster 
it must receive consideration here. (Decade iii, Canadian Organic 
Remains, Geol. Sur. Canada). In the third volume of the Palaeontology 
of New York, which appeared in 1861, Professor James Hall describes a 
