24 F. ' Chaprtian : 



arm almost halberd-shaped. The distal margin is twice notched, 

 and the proximal margin is circularly excavated, so that the 

 podial area is almost elliptical. The podial orifices are thus 

 represented in the negative cast by a double series of elliptical 

 to subquadrate rounded prominences, separated by the sinuous 

 ridge-like cast of the ambulacral furrow. The ambulacral ossicles 

 are fusiform and curved, the pointed proximal end being directed 

 inwards. The ambulacral canal is flexuose and bordered by the 

 curved inner margins of the ambulacrals. The ambulacral 

 ossicles are sometimes thicker than here drawn, and have the 

 notches more pronounced. The adambulacral plates are gener- 

 ally so close as to form an almost uninterrupted marginal border. 

 No trace of a disc has been detected in the specimens before us, 

 and the spines, if any, have not been preserved. 



Measurements of specimens in National Musenni. 



Spec. A. Spec. B. Spec. C. 



Length of arm - - - 20 mm. 24 mm. ? 



Diameter of arm at base - 3 mm. 2 mm. 3.5 mm. 



Diameter of arm near distal end 2 mm. 1.5 mm. ? 



Occurrence. — This species is of frequent occurrence in the 

 Silurian (Melbournian) sandstone of Moonee Ponds Creek, 

 Flemington. It also occurs rarely in the Yeringian series at 

 Yering. 



Genus — Gregoriura^ nov. 



Generic characters.— A Protasterid in which the usual boot. 

 shaped ambulacrals are laterally developed, and modified into a 

 subtriangular form. Ossicles on each side of the ambulacral 

 canal subalternate, excepting at the junction with the mouth- 

 frames, where they are parallel. Adambulacral ossicles narrow, 

 slender, extending laterally in a line with the proximal border of 

 the ambulacral ossicle. Spine-bearing plates, slender, at right 

 angles to the adambulacrals, carrying (in the genotype) two con- 

 spicuous spines. Oval skeleton having jaw-plates f the length of 

 the month-frames ; teeth thick and prominent. No traces of a 

 disc preserved in the specimen on which the genus is founded. 

 Arms very slender and very flexible. 



Named after Professor J. W. Greg-cry, F.R.S., who has devoted so much attention to 

 the elucidation and classification of this group of the echinodermata. 



