174 , THE ANNELIDA POLYCHAETA. 



more ventral one the larger. (Plate 19, fig. 7). Into the dorsal branch extends 

 a fascicle of acicular fibrillae, none of which protrudes from the surface. The 

 capillary setae are numerous, long and slender, and distaUy narrowing to a 

 very fine, acute and curved tip. 



Locality. Gilbert Islands: off Apaiang. Surface by electric Ught. Sur- 

 face temp. 84° F. 3 January, 1900. Three specimens taken. 



It is barely possible that this may be the female of A. obliquatus described 

 above, but whether this is so can be satisfactorily determined probably only 

 from material that wUl make possible a tracing of the sexual buds from the 

 stalk. The two forms resemble each other in the general structiue of the setae, 

 though differing in finer details, and in having alike six somites in the anterior 

 region bearing only composite setae; but they differ widely in aU other respects. 

 A very characteristic feature of this form is presented by the typical parapodia 

 in having two divisions strongly marked and well separated and divergent. 



Syllis Savigny. 



Descript. Egypte. Hist, nat., 1809 (= 1822), 1, pt. 3, p. 43; Grube, Archiv. naturg., 1850, 16, p. 309; 



Ehlers, Borstcnwurnicr, 1864, p. 220, 222; Langerhans, Zeitschr. wiss. zool., 1879, 32, p. 526; 



Malaquin, Rechcrches sur les syllidieiis, 1893, p. 71; McIntosh, British annelids, 1908, 2, pt. 1, 



p. 188. 

 Lycastis Savigny, Op. cil. 1809 [ = 1822], 1, pt. 3, p. 45. 

 loda Johnston, Ann. mag. nat. hist., 1840, .ser. 1, 4, p. 231. 

 Lalage F. Muller, Archiv. naturg., 1858, 24, p. 211. 

 Gnathosyllis Schmarda, Neue wirbellose thiere, 1861, 2, p. G9. 

 Trichosyllis Schmarda, Ibid., p. 73. 



Pagenstccheria Qdatrefages, Hist. nat. annel6s, 1865, 2, p. 40. 

 Aporosyllis Qu.\trefages, Op. cil., 1865, 2, p. 87. 

 ChadosylUs Malmgren, Annulata Polychaeta, 1867, p. 44. 



This genus was divided by Langerhans (Op. cit., 1879, 32, p. 527 ff.) into 

 four subgenera on the basis of the character of the setae. 



Key to Subgenera. 



a. Setae all simple Haplosyllis Langerhans. 



aa. Setae in part or exclusively composite. 



6. Setae all composite, vart-ing but little in size TyposyUis Langerhans. 



66. Simple setae also present or else composite setae of very different form or size. 



c. Li addition to the composite setae in all somites there are very different simple or composite 



setae Ehlersia Langerhans.' 



cc. Setae of the posterior somites composite, those of the middle or of the middle and anterior 

 somites siinple &ylli^ Savigny sens. sir. 



' The subgenus Langerhansia later added by Czerniawsky (Bull. Soc. imper. nat. Moscow, 1881, 46, 

 no. 2) is regarded as synonymous with Ehlersia. 



