INCERTAE SEDIS. 447 



Archaeocidaris scotica Young. 

 Archaeocidaris scotica Young, 1876, p. 230; Smith, 1901, p. 509; Laml>ort and Thidry, 1910, p. 1_'.Y 



This species is named from jaws, which are probably not generically or specifically recog- 

 nizable. They have not been figured. 



Lower Carboniferous, Craigenglen, Campsie, Scotland. 



Archaeocidaris selwyni 11. Ktheridgr, Jr 



Plate 15, figs. 9, 10. 



Archaeocidaris (?) selwyni R. Etheridge, Jr., 1892a, p. 67, Plate 15, figs. 1-3; Klem, 1904, p. 64. 

 Archaeocidaris sp. R. Etheridge, Jr., 1892a, p. 69, Plate 22, fig. 1 ; Klein, 1904, p. 65. 

 Archaeocidaris selwyni Lambert and Thiery, 1910, p. 12"). 



Known from nearly complete tests, but the spines are unknown. What position it would 

 take in relation to other species of the genus if we had the spines, is of course undeterminable. 

 Test large, fully four and a half inches in diameter at the greatest periphery. Ambulacra 

 narrow, plates low. Four columns of plates in an interambulacral area. The interambulacral 

 plates are very large and hexagonal, or in adradial columns pentagonal, and rounded on the 

 adradial suture, with very large primary tubercles. Etheridge says that the plates are in four 

 and perhaps five series. I see no indication of a fifth column in his figures, and as the other 

 species of the genus always have four columns in an area when this is completely known, it is 

 probable that selwyni has also (p. 257). Powerful jaws are present. Etheridge expresses ( he view 

 that the two specimens he figures belong to distinct species on account of the shape of the plates, 

 they being proportionately lower in the second and smaller specimen (my Plate 15, fig. 10), to 

 which he does not give any name. Unless further evidence develops, I think they can be safely 

 considered one species, the differences being ascribed to age, as the two differ considerably in size. 



Upper Marine Series, Permo-Carboniferous, the holotype from Nowra, Shoalhaven River. 

 County St. Vincent; the second specimen from the same horizon, about five miles south of 

 West Maitland, County Northumberland, New South Wales. 



Archaeocidaris sixi Barrois. 



Plate 10, figs, lla-llc. 

 Archaeocidaris sixi Barrois, 1882, p. 320, Plate 16, figs. 5a-5c; Lamlwrt and Thiery, 1910, p. 12:.. 



Known fragmentarily only from isolated plates and spines. Interambulacral plates 

 hexagonal; the height equals the width as figured. The spine is compressed, 6 mm. in 

 length, ornamented with fine vertical striae, and with a weakly defined annulus. On account 

 of the small size of the spine in relation to the interambulacral plates, also on account of the 



