[MATTHEW] STUDIES ON CAMBRIAN FAUNAS S3 



thorax ; also the eye-lobes are placed further back, and the marginal 

 fold is wider. They have seven joints in the thorax and six in the 

 pygidiura in the two species known. The genus appears to range across 

 the American continent, as a pygidium of this type has been found in 

 Newfoundland. 



Neolenus serratus, Roem. sp. 



Ogygia serrata, Roem., Acad. Nat. Sci., Phil., Proc. 1887, p. 13, pi. i., fig. 2. 

 Olenoides Nevadensis, (Meek), Wale, Am. Jour. Scl., vol. xxxvi., Sept., 1888, p. 165. 



The following is Roeminger's description of this species : " Head, 

 thorax and pygidium of equal length. General form of the head and 

 course of the facial sutures correspond almost completely with the 

 previously described species [Ogygia Klotzi]. The glabella of this form 

 is somewhat broader and more prominent than in the former ; also the 

 glabellar furrows are more distinctly marked ; they are three in number, 

 the hinder one is the largest, directed obliquely inward and backward, 

 but not reaching to the centre of the glabella. 



The palpebral rim and the rugosity continued from it upward across 

 the fixed cheeks are the same as in the former species. 



The movable cheeks are protracted into long slender spines, which 

 reach as far down as the fifth thoracic rib. 



Rachis broad, almost equal in diameter to the length of the correspond- 

 ing ribs, deducting their spiniferous prolongations. The occipital ring 

 terminates with a triangular monticulose prominence, overlapping the 

 first thoracic ring, and also each one of all these annuli of the thorax 

 and the pygidium bears a strong spine on the median line. 



The thorax of this species in all the specimens examined, composed 

 of only seven segments. 



The pygidium has five annulations, with as many ribs corresponding 

 to them. These ribs dilate considerably toward the margin, as in the 

 former [0. Klotzi'] ; but while in that a smooth rounded rim edges the 

 pygidium, in this form the principal ruga of each rib extends beyond the 

 margin of the pygidium under the form of a strong acute spine, directed 

 backward, so as to be almost parallel with the axis of the body. Five of 

 such spines fringe each side of the pygidium ; their size is gradually 

 diminished toward the posterior end. 



The hypostome in most of the specimens preserved, occupying its 

 natural position. 



One may add the following to Prof. Roeminger's description of the 

 characters of this species. The length of the three parts of the body is 

 somewhat shorter, going towards the tail-shield. The front of the head- 

 shield is shorter than in 0. Klotzi and so is the dorsal suture, the propor- 

 tion of the cords of the three curves along this line are for this si)ecie8 

 1, 1, 2, but for 0. Klotzi 1^, 1, 2|. 



