106 ox THE aENIJS CTENODTJS. 



G. Gorrugatus, Atthey, was discovered in the coal shales of 

 Northumberland. It was described by Messrs. Hancock and 

 Atthey in their " Notes," but it has never been figured. Its 

 characters are as follows (it must be remembered that my 

 descriptions of the teeth discovered and named by Mr. Atthey 

 are summaries of his remarks. I may state, however, that I 

 possess or have examined specimens of each of his species) : plate- 

 like ; thin ; sub-triangular ; three inches long, two inches broad ; 

 upper surface slightly convex, with nine stout, somewhat irregular 

 rounded ridges ; grooves wide and rounded ; ridges die out as 

 they approach the internal and external margins, but they are 

 slightly enlarged at the external extremities, and are indistinctly 

 and irregularly tuberculated ; inner margin nearly straight ; outer 

 border slightly convex ; anterior edge slopes forward from inner 

 margin ; posterior border produced and rounded ; surface 

 strongly and irregularly punctated. The distinguishing features 

 of this tooth are the fewness of the ridges, their roundness and 

 wide separation, its great size and general form, 



(7, octodorsalis, T. P. Barkas. From the Northumberland coal 

 seams, was described in the second volume of " Scientific 

 Opinion," but it was not illustrated. Its characters, according 

 to Mr. Barkas, are : — length, two inches ; width, one inch ; eight 

 ridges free from denticulations ; at the extremities of the first 

 six ridges there are slight depressions which indicate two rudi- 

 mentary tubercles ; the seventh ridge is drawn to a point, and 

 the end of the eighth ridge is flat and chisel-sha?ped ; the grooves 

 between the ridges are broad, and their bases are shallow and 

 smoothly rounded. 



C. concavus, T. P. Barkas, is only founded provisionally, for 

 its founder has occasion to think that it may be an unusual form 

 of C. tuberculatus. It was discovered in the Coal Measures of 

 Northumberland. The tooth is 2| inches long, li inch broad, 

 very concave from without inwards, and presents the appearance 

 of a large segment of a cylinder ; the external edge is nearly 

 straight ; the internal margin resembles the side of an ellipse ; 

 the ridges are eleven in number, and extend across the body of 

 the tooth at right angles with the front ; the ridges are deep, 

 angulated, and slightly curved ; the anterior ridges are broad, and 

 the remainder gradually narrow towards the posterior extremity 

 of the tooth ; except at the external extremities of the ridges, 

 they are free from tuberculations ; the crest of the anterior ridge 

 is very convex, the others very concave ; anterior ridge has two 

 well-developed and two rudimentary tubercles ; the second three 

 well-defined ; third, fourth, fifth, sixth, seventh, have one each ; 

 the eight has two, and the remaining ridge one ; each external 

 tubercle on first, second, and eighth ridges are covered by 

 brilliant cream-coloured enamel ; the rest 'are dark, and highly 



