254 DODECACERIA. 



Prom the peristomial segment the body gradually widens to the eighth or ninth 

 bristled segment, and then rather abruptly dilates into an ovoid enlargement of ten 

 segments, when it again contracts, snch in all probability being due to the mode of pre- 

 paration. The segments of the anterior region are distinctly marked and one-ringed, and 

 the feet are represented by lateral ridges with dorsal and ventral setigerous processes and 

 a minute flat intermediate papilla. Anteriorly the feet present, as at the sixth, a long 

 dorsal tuft of capillary bristles and a shorter one ventrally (Plate OIX, fig. 14). This 

 arrangement continues toward the thirtieth foot, when a stouter series appears— at first 

 simply modified ordinary bristles with a double curvature of the shaft and a finely tapered 

 tip, the ventral series apparently preceding the dorsal. Finally, posteriorly both divisions 

 have the elongated and characteristic hooks (Plate CIX, fig. 14 a). These have long, 

 straight, finely striated shafts, which at the upper part have a slight bend forward, and 

 then gently curve forward to the sharp tip, the striae ceasing about the middle of the latter. 

 They thus differ from the condition in Ghoetozone and approach that in Oirratulas. 



I am indebted to Mr. Southern, who is specially engaged with the Cirratulids, for 

 drawing my attention to the affinity of this form with Levinsen's Cirratidus caudatus, and 

 there is certainly nothing in the description of the forms which seriously differs. No 

 figures were given by the Danish author. 



Genus CVII. — Dodecacebia, 1 GErsted, 1843. 



Head conical, mouth sub-terminal. Buccal segment with dorsal branchiae and two 

 grooved tentacles. Body linear, rounded. Filiform branchiae placed singly on each side 

 in five or six anterior segments, in some none, but the number is comparatively small. 

 Feet with capillary dorsal bristles, and hooks interiorly. No posterior appendages. 

 Bristles partly capillary, partly short and thick, somewhat uncinate. 



In Dodecaceria concharum the glandular hypoderm is largely developed, but the nerve- 

 area is small and flattened, having to its exterior the slightly-developed circular muscular 

 layer, the basement- tissue, the hypoderm, and cuticle. The longitudinal muscles are almost 

 continnons, and proportionally thicker than in Cirratidus. The inner ends of the ventral 

 come close to the nerve-trunks (Fig. 126). 



CErsted (1844) included Dodecaceria as one of the genera of his Aricide lumbricinse, and 

 Grube (1851) followed a similar arrangement in his ' Families of the Annelids.' 



De Quatrefages (1865) adopted the Heterocirrus of Grube for this genus, and one of 

 the generic characters was the presence of eyes, another the presence of a large tentacular 

 cirrus above the branchiae in the first segment. Moreover, he conserved the genus Nar- 

 ganseta of Stimpson, which does not appear to differ in any marked degree from 

 Dodecaceria. 



Monticelli (1891) gives a description of Dodecaceria concharum, stating that it is 

 hermaphrodite, the male elements occurring first, and the female subsequently from the 

 sixth segment backward. 



1 AwcWt and Ke^aia, antennae? 



