Silurian.] PALEONTOLOGY OF VICTORIA. [Asteria. 



Plate X., Figs. 2, 3. 



URASTERELLA SELWYNI (McCoy). 



[Genus URASTERELLA (McCot) = STENASTER (Billings). (Class Echinodermata. 

 Order Astcri^. T"am. Urasteridce.) 



Gen. Char. — Small starfishes, with five moderate rays, narrowed at the base, and without 

 disc. Ambulacral grooves narrow, bordered on the under side, with only one row of large 

 (adanibulacral) plates ; no marginal plates. Upper surface with numerous rows of small 

 tubercular plates. Confined to Silurian rocks.] 



Description. — Rays 5 elongate g-radually tapering' from a little beyond the 

 base, which is slightly contracted, angulated on the upper side bj' a prominent ridge 

 along the middle of each ray, having a row of conical tubercular plates (about 8 in 

 2 lines), each side sloping on the dorsal aspect from the middle with about 3 rows 

 of conical tubercular plates rather smaller than the middle row. The 5 axil plates 

 small, ovate, triangular, very tumid. Adambulacral plates large, extending to the 

 tubercular margin, transversely oblong, about twice as wide as long (about 9 in 2 

 lines). Ambulacral plates small, in a deep ambulacral groove. Length of ray from 

 mouth to tip, 6 lines; greatest width near base, 1^ lines. Surface of plates 

 granular. 



The late Mi-. Salter and Mr. Billings refer the starfishes of this 

 type to the subsequently published genus Palceaster of Hall ; but, 

 as Professor Hall objects that his genus Palceaster has ambulacral, 

 adambulacral, and marginal plates, and the types of my genus 

 U. Ruthveni and U. hirudo of the English Ludlow rock, like our 

 Australian species and the American Palceaster or Stenaster 

 pulcliella^ have only one row of j^lates on each side of the ambu- 

 lacral groove, I return to the use of my old generic name, of which 

 Stenaster of Billings seems a synonym. 



This beautiful species is easily known by its strongly angulated 

 rays on the dorsal side. The traces of oral plates are so very 

 minute and indistinct that I cannot give their character. 



This is the first fossil starfish seen in Australia, and I dedicated 

 it to my old friend Mr. Selwyn, formerly Director of the Geological 

 Survey of Victoria, and now Director of the Geological Survey of 

 Canada, who collected it. 



Common in the fine sandy Sihu'ian beds of range on E. side of 

 commonage reserve, Kilmore. 



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