ART. 9. A POLYCHAETOUS ANNELID TREADWELL. 3 



the latter tuft, occupying the middle region, is a smaller group of 

 setae with terminal joints shorter than in the other type, with 

 blunt ends and long marginal teeth (fig. 5). Both forms of setae 

 have camerated shafts. In the sexual region of the male I found 

 only one type of seta, having the broad flat, paddle-shaped terminal 

 joint with one margin toothed, which is characteristic of heterone- 

 reids. The form and arrangement of setae in the female is essen- 

 tiallj^ like that in the male, except that in among the paddle- 

 shaped setae of the sexual portion I found a few of the long type, 

 like Figure 5. There would be one or two of these in each half of 

 the parapodium. I did not determine whether they are present in 

 all of the sexual parapodia but they appeared in those from near the 

 middle of the body. I could find none of these in the sexual region 

 of the male, but the material at hand was not sufficient to enable 

 me to decide whether this is a sex difference. 



The jaws are rather heavy, translucent-brown in color each with 

 about 10 teeth. Paragnaths are arranged as follows: I, 3 or 4; 

 II, about 20 arranged in approximately 3 diagonal rows ; III, about 

 30 on either side, arranged in the form of a curved triangle, 4 or 5 

 paragnaths wide at the base and narrowing tow^ard the apex, the 

 terminal 2 rows made up of one paragnath each; IV, about 30 in 4 

 (approximately) transverse rows; V, usually 3 in a longitudinal 

 row, but 2 specimens had only 1 each ; VI, a circular patch of about 

 9 on either side ; VII, a single row on either side, which toward the 

 ventral end becomes double and merges gradually into VIII, which 

 has 3 transverse rows, of which the 2 anterior are of much larger 

 paragnaths than are found in the posterior one. 



The male holotype (Cat. No. 19095 U.S.N.M.) and female para- 

 types (Cat. No. 19096 U.S.N.M.) are in the collections of United 

 States National Museum. 



EXPLANATION OF PLATE. 



Fig. 1. — Anterioi- i-egion of female XIO. 



2. — Parapodium from anterior region of male X28. 



3. — Parapodium from the sexual region of male X2S. 



4. — Seta from anterior region of male X250. 



5. — Second form of seta from anterior region of male X2.50. 



