236 Messrs. E. Etlievidge, Jun., ancIV. H. Carpenter ou 



unci terminating around the moiitli in blunt processes. Am- 

 bulacra lanceolate-petaloidj tapering but little, A\'ith a well- 

 marked food-groove, and another groove on each side sub- 

 parallel to it. Lying on the lancet-plate between the food- 

 groove and these lateral grooves are the side plates, that 

 portion of the ambulacra outside the latter being in all proba- 

 bility firmly anchylosed outer side plates ; pinnule-sockets 

 large. Hydrospire-slits seven in number in each interradius, 

 half exposed, and one covered by the edge of the adjacent 

 ambulacrum. Mouth very small; anus rhomboid. Surface 

 smooth in the example under examination, but probably 

 ornamented by striaj following the margins of the plates. 



Ohs. We are indebted for this interesting species to our 

 friend Dr. G. J. Hinde, who believes it to be identical with 

 Cadaster canadensis, Billings (MS.)- The few remarks* 

 made by Mr. Billings about C. canadensis are quite insuffi- 

 cient for its identification ,• and we have therefore much 

 pleasure in associating our specimen with the name of its 

 discoverer, who lias so earnestly worked in the field of 

 Canadian palaeontology. 



The form of the radial plates, irrespective of other charac- 

 ters, at once distinguishes C. liindei from C. pyraviidatiis, 

 Shumard, and therefore probably also from C. americanus of 

 the same author. The diagnosis of C. Whitei, Hall, partakes 

 more of a generic than of a specific character; but it also 

 appears to be a distinct species. The length of the radial 

 sinuses and ambulacra, and the angle at which they are 

 inclined to the general plane of the summit, sharply distin- 

 guish C. alternatitSj l-^yon, from C. Hindei, and give the 

 two species a very different appearance. Furtlier, in the 

 summit of the former, when viewed from above, portions of 

 the inturned upper edges of the radial plates are visible ; but 

 in C. Hindei the perpendicular position of the sides of these 

 plates quite prevents their appearing on the ventral aspect, 

 where nothing is visible but tiie true summit-characters. 



Log. and Horizon. Arkona, Ontario, Canada. Hamilton 

 Group, Upper Devonian (Coll. G. J. Hinde, Ph.D., F.G.S.). 



Genus Geanatockixus (Troost, 1850, MS.), Meek & 

 Worthen (redef. E. <& C. 1882). 



Orbiiremites, J. E. Gray (MS.), Syuop. Brit. Mus. 1840, p. G3. 

 GraHutvcrinites, Troost (MS.), Proc. Amer. Assoc, xldv. Science for 

 1849, p. G2. 



* Amer. Jcurn. Sc. l8l')9, xlviii. p. 7'J. 



