CNEMID ACTINIAE. 155 



are stated to be "arranged in a few concentric rows," obviously an advance on the 

 usual primitive " Urasterellid " arrangement. Schuchert regards this species as 

 descended from U. pulchella. I am not able to see any good grounds for this 

 opinion. The specimens are found in the Richmond (Upper Ordovician) for- 

 mation. 



U. huxleyi, Billings, described by Schuchert (85, pp. 182 — 183). — Schuchert 

 states that : " The abactinal side of the disc has a central disc plate that is large 

 and tumid. Around it is a circle of six smaller, highly convex plates, and at the 

 base of each ray medially there is another single large tumid plate, the basal radial 

 [obviously the primitive ' Urasterellid ' arrangement]. The abactinal side of the 

 rays is highly convex and somewhat angulated medially. [This latter character 

 distinguishes it from S. asperrimus.~\ The ossicles are small and distinctly arranged 

 in quincunx, of which there are about six plates in each diagonal row near the 

 base of a ray . . . all the ray ossicles are of equal size. R : r : : 58 mm. : 5"5 mm." 



The only specimen was found in the Chazy (Middle Ordovician) beds at Point 

 Rich, Newfoundland, and is now in the Ottawa Museum. 



Australian Species of Salteraster. 



Salteraster ? sehvyni was described as UrastereUa selwyni by McCoy (Geol. Surv. 

 Victoria, Prodr. Palasont. Victoria, dec. i, 1874, p. 42, pi. x, figs. 2, 2a, 3, 3a). The 

 figures and description suggest that the species might really belong to Salteraster, 

 but good structural details are not given. The form is said to be " common in the 

 fine sandy Silurian beds of range on E. side of commonage reserve, Kilmore." 



Family Cnemidactinidj:, nova. 



1914. UrasterellicLv, Schuchert (pars), Fossilium Catalogus, Animalia, pt. 3, p. 7. 



1915. „ Schuchert, Bull. 88, U.S. Nat. Mus., p. 172. 



Group C forms with arms margined by closely-knit adambulacralia and 

 infero-marginalia. Both these series of plates covered by a uniform ornament 

 of small spines. Apical plates of disc irregularly arranged. 



The family is founded for one genus and species, Gnemidactis girvanensis 

 (Schuchert), forms of which are found in considerable numbers in the Upper 

 Ordovician (Ashgillian) of Thraive Glen, Girvan, Ayrshire. This abundance, with 

 the large comparative size of the specimens, suggests that one has to deal with a 

 type which has reached the maximum stage of its lineage, or, in other words, that 

 we have to deal here, exactly as was the case in regard to Promopalseaster, with a 

 genus which has already passed through various stages not at present known 

 because of the imperfection of the geological record. We should expect to find 



