RAYMOND: NEW AND OLD SILURIAN TRILOBITES. 25 



Barrande, and, on the other hand, thou.^h the pygidia in the Day 

 collection are much like that of A. portlocki, their cephalons are very 

 unlike those assigned to A. portlocki by Barrande. 



Formation and locality: — The specimens figured are from the 

 Niagaran at W,ajiwatosa, Wise. 



ENCRINURIDAE Angelin. 



Encrinurus reflexus, sp. nov. 

 Plate 3, fig. 7, 8. 



The Day collection contains several pygidia of an Encrinurus which 

 is larger and differs in various ways from any species of this genus 

 heretofore described from Silurian strata of this country. 



Cephalon and thorax unknown. 



Pygidium large for the genus, triangular, pleura bent abruptly 

 downward, the posterior end somewhat turned up. Axial lobe very 

 long, tapering backward to a point. It is marked by about thirty 

 rings which are prominent and sharp toward the front, but very faint 

 at the posterior end. With the exception of two at the anterior end 

 the rings do not cross the axial lobe, but leave a narrow smooth space 

 along the median line. Along this smooth lane are disposed eight 

 pustules, approximately evenly spaced. On the pleural lobes are 

 eight pairs of broad flat ribs which curve backward, making a rather 

 abrupt turn near their outer ends. They do not reach quite to the 

 margin, and end in blunt free spines which project from the sides a 

 little above the margin. At the posterior end the last two ribs from 

 each side converge alongside the axial lobe, and, with a small median 

 spine, project beyond the end of the axial lobe. The ribs have small 

 pustules scattered somewhat irregularly over them, and not aligned 

 in longitudinal rows. Nearly every rib has a pustule at its inner end 

 •and one near the middle. Some of the ribs have only these two, but 

 the longer ones near the front have another. 



Measurements: — The more complete of the cotypes is 28 mm. long, 

 26 mm. broad at the front. The axial lobe is 9 mm. wide at the front 

 and 26 mm. long. 



Comparison with other species : — Nine species of Encrinurus have 

 previously been described from the Silurian of America, but most of 

 them are of much smaller size than the present species and only two 



