OLENELLUS AND OTHER GENERA OF MESONACID.E 335 



Dimensions. — The largest cephalon has a length of ii mm., width 

 20 mm. The proportions of the various parts are shown in the photo- 

 graph of an entire cephalon illustrated by fig. 5. pi. 41. 



Observations. — 0. logani is the Atlantic Province representative 

 of O. fremonti [pi. 37] of the southern Pacific Province area. It 

 differs from O. fremonti in minor details of the glabella, especially 

 the furrow and smaller lobes, in its proportionally larger eyes, and 

 in the regular form of its genal angles. It has larger eyes than 0. 

 canadensis [pi. 38]. 



Formation and Locality. — Lower Cambrian : L'Anse au Loup 

 limestone at L'Anse au Loup, Labrador, on the Straits of Belle Isle, 

 Canada. 



Type specimens in the Museum of the Geological Survey of 

 Canada. 



OLENELLUS RETICULATUS Peach 



Plate 39, Figs. 9-13 



Olencllus reticidatus Peach, 1894, Quart. Journ. Geol. Soc. London, Vol. 

 50, pp. 665-666, text fig. A, p. 673, pi. 30, figs. 1-6, 8-14; pi. 31, figs. 1-7. 

 (Described and illustrated, most of the description being copied below. 

 The specimens represented by figures i and 2 of plate 30 are redrawn 

 in this paper, pi. 39, figs. 9 and 10.) 



Dr. Peach, in comparing this species with its most nearly related 

 form, O. lapworthi, says, after stating that it is of larger size: 



The reticulated ornament on its test appears to be much larger in pattern 

 (compared with its size) than in that species, and this difference, which makes 

 it conspicuously visible to the naked eye, has suggested the specific name which 

 I propose for the new form. In general aspect it much resembles the elongated 

 variety of O. lapworthi. It differs from that chiefly in the head-shield, which is 

 deeper in comparison with its breadth. The glabella is longer in proportion 

 to the size of the head-shield, and the individual lobes are each more elongated, 

 while the angles made by the furrows with the general axis of the body are 

 more acute. The distal ends of the eye lobes are not so far removed from the 

 edge of the glabella, nor do they e.Ktend so far backwards, but end well in 

 front of the fourth furrow, while those of O. lapivorthi extend beyond it. The 

 raised margin that bounds the cheeks is not so wide in proportion ; the genal 

 spine is more slender, and is placed a little more anteriorly, and the notch 

 between it and the pleural an^e is deeper than in O. lapivorthi. 



The arrangement of the details of its body-segments is similar to that of O. 

 lapivorthi, but the peculiarities of the pleura of the third segment are even more 

 pronounced, the spines being longer relatively, and sometimes more incurved. 

 The spines on the pleura of the sixth and three succeeding segments are longer 

 and more slender. Tubercles have been observed in the mid-line on the occipital 

 ring, on the axes of the first three free segments, and on several of the posterior 



