POTTS—POLYCHATA: AMPHINOMIDA. 369 
dorsal setee so carefully described and figured by Gravier have been recognised. In 
addition, a fourth type is found in the anterior segments (cf, Pl. 46. fig. 19), a slender 
distinctly furcate seta with, however, one ramus much more elongated than the other. 
By suppression of the shorter ramus it passes into the subfurcate type, which alone is 
present in the posterior segments, and in some of the anterior segments intermediate 
forms are found. The subfurcate type of bristle as figured by Gravier (text-figure 262) 
is essentially the characteristic type of this group of species. 
Localities :— 
(1) Rotuma, Fiji. 
(2) Funafuti: 1 bottle with large specimens, largest 54 cms. ; 1 bottle with moderate- 
sized specimens ; some smaller specimens in tubes show serrations, and are therefore 
E. pacifica. 
(3) Maldives: Hulule, Male Atoll, large number of specimens of all kinds ; Goidu, 
Geifurfchenchi Atoll, one set of specimens is interesting for the rather marked de- 
velopment of the dorsal setee, which are white and silky; Velu, Funado, Miladamadulu 
Atoll, another specimen with silky dorsal sete ; Minikoi, Laccadives, specimens of all 
kinds. 
(4) Chagos: Salomon Atoll; and Ile du Coin, Peros Atoll. 
(5) Seychelles, Coetivy. 
16. Eurythoé heterotricha, sp.n. (Plate 45. figs. 16,17; Plate 46. figs. 18, 19.) 
Measurements. Length 60 mm., breadth 3°5 mm.; no. of segments 65. 
The body is slender, rectangular in section, but not so flattened as in #. complanata, 
and unpigmented. The caruncle is minute, only extending back to the end of the 
second segment. ‘The head is large and oval, and two pairs of eyes are situated upon it, 
the anterior being larger. A slender median tentacle stands equidistant from both 
pairs. The lateral tentacles are stouter and about the same length. There are three 
buccal segments. 
The gills begin on the third body-segment as a simple fureate process. In the next 
segment there are four branches, but the branchie never attain to a very full 
development, reaching their limit in the middle with about fourteen branches, 
A characteristic appearance is imparted to the annelid by the setz, which are silky and 
are arranged in compact bundles, fraying out at the ends on account of the exceptional 
length of a few of the sete (Pl. 45. fig. 17). The dorsal representatives mainly consist of 
two types, a straight symmetrically tapering serrate seta as found in other species * 
and a furcate type figured (PI. 46. fig. 19). The presence of such a seta has just been 
remarked in the anterior segments of 2. complanata, but it has been pointed out that 
it passes there into a subfurcate type. No such modification takes place, however, in 
this species, but the furcate type is present throughout the body and the subfurcate 
type is absent dorsally. The specially long sete are derived from the furcate type 
by the excessive elongation of the outer ramus of the fork, which attains to a 
* They do not appear to be so distinctly and eyidently serrate as in HZ, complanata. 
SECOND SERIES.—ZOOLOGY, VOL. XII. 50 
