190 ROYAL SOCIETY OF CANADA 



DoRYPYGE HORRiDA, n. sp. (PI. IV., figs. 3a and b.) 



Head and thorax unknown. 



Pygidivini elongate-subtrapezoidal, with prominent rachis, rather 

 flattened side lobes and recurved border. Raehis of six convex annula- 

 tions, of which the first four are crowned by spines, the fifth by a 

 tubercle, and the sixth is short. Lateral lobes marked by five broad 

 shallow furrows, which diverge in a fan-like manner. Pygidium 

 bordered by a flattened margin having the outer border recurved and 

 fringed on each side with six spines directed somewhat backward and 

 upward ; of these spines the penultimate pair are longer than the others. 



Sculpture. — The surface viewed with a strong lens appears minutely 

 tuberculate. 



Size. — Length of this j^ygidium, exclusive of the spines, 4i mm.; 

 width, exclusive of the spines, 8 mm. 



Horizon. — Phosphate nodule in a limestone band of the gray shales. 



Owing to the strong spinous rachis of the pygidium, I was at first 

 disposed to think this a young stage of JD. Marcoul Whitfield sp., which, 

 indeed, it may possibly be ; for although Mr. Whitfield estimates a pos- 

 sible ten segments in lus species, this is beyond the analogy of other 

 sjiecies of the genus, and the number of rings shown in the rachis of the 

 P3'gidium which he figures as defective may be the complete number ; 

 even then, however, it has one segment more than the normal number, 

 or than the St. John example. Owing to this and some differences of 

 form it seems desirable to assume that the latter is a distinct species. 



The St. John pygidium seems to come nearer in form to the example 

 figured by Mr. Walcott as Olenoides, Marcoui, but he represents the 

 species as smooth on the rachis of the ])ygidium, which is certainly not 

 the case with the St. John form, Waicott's trilobites are therefore of 

 another species ; one is figured with six, the other with seven spines on 

 each side of the pygidium.' 



Since Bulletin 30 was issued Mr, Walcott has described another 

 species of Dorypyge (^Olenoides Fordi)- which with a rachis having a row 

 of tubercles along the summit, has a narrower pygidium and spines 

 directed backward ; it is aboiit one and a h:ilf times as long as our 

 species, and more convex. It is from Washington County, New York, 

 and occurs with ElUptocephala asaphoides. 



List of the Species. 



The following list will show in brief the relation of this fauna to the 

 corresponding faunas in other lands. As has been remarked, this is 



1 U, S, Geol. Surv. Bull,, 30, pi. xxvi,, figs, ^a and 5b. 



2 Faunti of the Olenellus Zone, pi, xciv,, figs, 3, 'Sa and h. 



