Dr. H. Woodward — M. Cambrian Fossils of the Rockies. 535 



but of this species I have not seen the original specimen, only the 

 figure. Dr. G. F. Matthew (op. cit.) is probably justified in 

 separating this form from Olenoides, but it is very difficult to decide 

 whether the imperfect specimen figured and described by Walcott 

 as the Olenoides Nevadensis of Meek is identical with Eominger's 

 0. serrata. 



Length of largest entire specimen in Mr. Whymper's collection 

 6 cm., breadth 4 cm. (Dr. Eominger gives the size of his 

 specimen as 7 c. long and 5 c. wide.) The head is 21 mm. long, 

 the seven free and movable thoracic somites also 21 mm. long, 

 and the pygidium 17 mm. long ; the glabella is 13 mm. broad at the 

 cervical furrow, and increases 15 mm. in breadth in front. Three 

 lateral furrows divide the glabella into four lobes on each side ; the 

 fixed cheeks form a frontal border separating the glabella from the 

 margin of the head-shield, which is slightly raised ; they (the fixed 

 cheeks) are broader near the front of the head, and contract slightly 

 in front of the eyes, when they expand again to form the ocular 

 lobes ; then, after a slight contraction, they expand to form an acute 

 angle laterally in uniting with the pleurse of the cervical ring. The 

 free cheeks are somewhat narrow, and produced to form the lateral 

 spines of the head-shield, which extend backwards to the fourth 

 segment ; the eyes are small and narrow, and unite with the 

 glabella by a distinct ocular ridge at their front angles. The axis 

 of the neck-furrow is as broad as one of its pleurae ; the seven free 

 thoracic rings have a strongly marked axis, which gradually 

 diminishes from 13 mm. behind the neck-lobe to 9 mm. in front 

 of the pygidium ; the pleurae are as wide as the axis, broad and flat, 

 with a strongly marked pleural groove, and at the fulcral point, 

 which is clearly marked, their extremities are bent sharply back, 

 and are produced into spines which overlap one another and 

 become slightly broader posteriorly; the five coalesced somites of 

 the pygidium are much expanded and end in strong marginal 

 spines. There is a central tubercle (or, according to Rominger, 

 a short spine) upon the axis of each somite and five upon the 

 pygidium. The hypostome (figured by Eominger) is rounded 

 shield shape (see op. cit., pi. i, figs. 26, c). 



"The species," says Dr. G. F. Matthew, "included in the new 

 genus (Neoleniis) are closely related to Parabolina (Salter, 1849) ; 

 they differ chiefly in having a longer pygidium and shorter thorax ; 

 also the eye-lobes are placed further back and the marginal fold is 

 wider." 



After a comparison of Dr. Matthew's figures of Parabolina (in 

 Fauna of St. John's Group, Trans. Eoy. Soc. Canada, 1891, vol. ix, 

 p. 51, pi. xiii, fig. 5) I am led to the conclusion that the St. John's 

 specimens are too fragmentary for comparison with our Mount 

 Stephen examples, and do not assist in arriving at such a conclusion. 

 Nor can the present species be placed, as Dr. Eominger believed, 

 near to Ogygia Klotzi, save as one of an already well-differentiated 

 group of genera and species of Cambrian Trilobites. 



