NO. 5 MIDDLE CAMBRIAN ANNELIDS 1 15 



The posterior section is a little more than one-third the entire 

 length of the animal. Posteriorly it grows smaller and terminates in 

 a rounded end. 



Surface. — The surface of the anterior and central sections is 

 marked by numerous distinct, annular, impressed lines that divide 

 it into many segments or metameres. In a specimen 26 cm. in 

 length the annular lines average two to the millimeter along the 

 anterior half of the body (fig. 3), while the posterior half is ap- 

 parently smooth (fig. 5). Numerous fine setae occur on the poste- 

 rior end of the body. The smooth surface may be due to the con- 

 dition of preservation, as some specimens of the anterior half show 

 no traces of annular rings or segmens. From the mouth backward 

 for a distance equal to four or five times the diameter of the flattened 

 body the surface is thickly studded with elongated papillae, as shown 

 on the left side of figure i. The papillae appear to be arranged in 

 longitudinal rows. 



Parapodia. — Small, branching parapodia fringe the side of the 

 body on several specimens (figures 4 and 5). There appear to be 

 two, three, or even more divisions of some of the podia. 



Proboscis. — A single specimen shows the proboscis protruded 

 (fig. i). It is slender and expanded toward the outer end where the 

 surface is covered with numerous fine papillae. The posterior half 

 has many fine setae extending obliquely forward. In fig. 3 the 

 proboscis appears to have been retracted within the body and more 

 or less crowded in on itself. 



Month and amis. — The mouth is circular and surrounded by rows 

 of strong setae (figs, i and 3). No teeth have been seen. The anus 

 is probably terminal as the enteric canal may be traced to within a 

 very short distance of the posterior end of the body. 



Enteric canal.- — This canal is a rather large, elongated tube that 

 extends from the mouth to the anus. It appears to be straight with 

 an expansion at about the anterior third (fig. 2) that is quite marked 

 in several specimens. In some examples the canal appears to be 

 constricted by annular lines that divide it into segments two to three 

 times as long as the segments of the body. There is a suggestion in 

 one specimen that the body cavity was divided into a series of 

 chambers by delicate muscular bands, but to be conclusive such an 

 interpretation should be substantiated by evidence from other speci- 

 mens. 



Observations. — This beautiful annelid was first recognized from 

 the specimen illustrated on pi. 18, figs, i, 2 and 5. It was found 



