STRATIGRAPIIICAL DISTRIBUTION. 27 



Palasterina stellala, Billings. Geol. Siirv. of Canada, Organic Remains, decade iii, 



pi. ix, fig. 1, p. 7C. Fig. IG b copied from this plate. 



Description. — Pentagonal ; disc about one half of the whole diameter ; ambulacral 

 grooves narrow and deep, bordered on each side by a row of small, nearly square adam- 

 bulacral plates ; a second row, consisting of disc-plates, extends nearly to the end of each 

 ray, the remainder of the disc covered with smaller plates. All these plates are solid 

 and closely fitted together ; the disc-plates in the angles in contact with the oral plates are 

 much larger than any of the others (fig. 16 «). 



In the only specimen in the collection, the length of the rays, measured along the 

 ambulacral grooves, is three lines ; number of adambulacral plates on each side of the 

 grooves, si.xteen ; the rays diminish somewhat rapidly in size, and terminate in a rounded 

 point ; diameter of the disc four lines. The plates are all a little worn, so that the cha- 

 racter of^their surfaces cannot be observed; they were probably nearly smooth. 



Locality and Formation. — City of Ottawa ; Trenton Limestone. Collected by Dr. 

 Billings. 



Palasterina rugosa, Billings. Geol. Surv. of Canada, Organic E.emains, pi. ix, figs. 



2 «, h, c, p. 77. 



Description. — Two inches in diameter ; rays five, acute at their apices, and rapidly 

 enlarging to a breadth of four lines at the disc, which is eight lines in width. The 

 specimen shows the upper side of the fossil only. Some of the plates are absent from the 

 centre of the disc, but those which remain are very prominent in their centres, and roughly 

 ornamented with four or five deep crenulations or furrows from near the centre to the 

 edges, producing a star-like appearance, resembling a half- worn plate of Glyptocrimts 

 decadactylus ; their diameter is from one to two lines. 



The rays are composed (at least, the backs and sides of them) of four rows of plates, 

 which are so very prominent that they appear to be almost globular, and even pointed in 

 their centres ; the central rows are the smallest ; the first four plates of the outer row 

 occupy three lines in length, and of the inner rows nearly as many. Towards the point 

 of the arm all diminish rapidly in size. Beneath the outer rows two others can be seen, 

 which are probably the outer marginal plates of the under side, corresponding to those 

 of P. riyidus. 



Locality and Formation. — Charleton Point, Anticosti ; Hudson River group. Col- 

 lected by J. Richardson. 



1 'Geological Survey of Canada.' Canadian Organic Remains, decade iii, p. 1^, pi- ix, tig. 1-15. 



2 Ibid., p. n, pi. ix, fig. 2. 



