neio "Worm" from Lower Ludlow Beds. 127 



and oniMineiit becoming obscure. The total Iciigtli is 60 mm. 

 (abiuit 2J inches). It is thus seen that, tliougli the length is 

 no greater than the mean length of the Aineiican specimens, 

 the absolute width is half as much again as in the widest of 

 them ; iience the trivial name proposed. 



The segments (fig. 2) are not very convex, but they are 

 separated by well-detined grooves, and — as a rule, at any rate — 

 each bears two lines o£ papilla). This at first sight gives tlie 

 ap))earance of two segments, but the median groove between 

 the lines of papillae is less marked tlian that between the 

 segments. In each segment it is frequently the case that 

 one line of papillae is stouter than the other, so that there is an 

 apj)earance of alternately large and small segments, much as 

 in a crinoid stem with alternating columnals. If the feebler 

 line of papillaj became still slighter or were pushed under the 

 next segment, then the appearance would be that of equal 

 segn)enfs each with a single line of papillse. Such is actually 

 the a[)[)earance towards the ends of the specimen, which there- 

 fore in this respect agrees with P. ornatus. In P. magnus 

 only one line of papilla? to the segment has been observed 

 throughout. 



No definite arrangement of the papillse in longitudinal 

 series, either linear or alternating, is immediately obvious; 

 but where the segments are least disturbed and the papillae 

 most orderly there is a suggestion of oblique lineation, and 

 this would probably be plainer if the two lines of papilla? 

 were of equal strength. 



Where the segments are clearly seen, and the two lines of 

 papillte fully developed, about four segments occupy 1 mm., 

 so that the height of twelve segments equals the width of the 

 specimen, i. e., a ratio about 8/100. The absolute height of the 

 segments agrees fairly with that stated for P. ornatus, but the 

 relative height is less than that of any species, the next in 

 order being P. magnus. The total number of segments in the 

 individual is about 275. Correlated with the greater width of 

 the specimen is the increased number of papillie in a line — 

 namely, from eighteen to twenty on one side of the compressed 

 tube, which is half as many again as in P. ornatus, three 

 times as many as in P. magnus. 



Tiie most noteworthy feature of this sj)ecin)en is a thick- 

 ening along the median line, extending through the whole 

 curved head of the 2 to within 2*5 mm. of its end, and 

 reaching down the stem to a point about 23 mm. from the 

 other end. On the imprint, in each counterpart, this tiiiek- 

 ening appears as a groove, about 0*5 mm. wide, and of 

 rouglily semicircular section. In some places the bottom of 



