128 
THE VOYAGE OF H.M.S. CHALLENGEE, 
In transverse section the body-wall is invested by a well-marked cuticle, thickest 
ventrally, especially in the middle line. The hypoderm, on the other hand, is very thin. 
The dorsal longitudinal muscles are peculiar, for they are continued as a thick mass to 
the middle line anteriorly, where they almost touch, being only separated by strong 
vertical bands of muscular fibres which pass downward. The ventral longitudinal 
muscles are not much thickened externally, and only moderately diminished internally. 
The ventral area is well marked, a considerable interval occurring between the obhque 
muscles. The cords are somewhat flattened, and have superiorly a thin stratum of 
longitudinal muscular fibres. 
In the sections the proboscis has been cut posteriorly. The external longitudinal 
muscular layer is very powerful, and between it and the great internal glandular coat a 
thin stratum of circular fibres occurs. 
A few minute ova appeared at the bases of the feet. 
The Polynoe vittata of G-rube,^ from Sitka, is an allied form with forty-three pairs of 
scales. Commensalism, indeed, seems the rule in those most nearly related. The 
Ilalosydna lordi of Baird,^ a pale species from Vancouver Island, lodges between the 
mantle and foot of Fisurella cratitia, Gould; while another very fragile form [Halosydna 
fragilis, Baird ®), ajoproaching AcJdoe, frequents a Starfish in the same region. Another 
allied form, the Lepidametria commensalis, Webster, lives in the tubes of Amphitrite 
ornata, Verrill,'* on the Virginian coast, and it has scales extending throughout the entire 
length of the body. Like all the preceding, it also has dorsal bristles. Other forms, 
such as the Polynoe rutilans ® of Grube, are shorter, with only fifteen pairs of scales. 
The species just mentioned was found on Xe7iia, an Alcyonarian from the Philippines. 
Dr. Baird ® also mentions that a variety of Harmothoe imhricata lives in the tubes of 
ChcBtopterus insignis, Baird, at the Menai Straits, near Beaumaris, but an examination 
of the preparations in the British Museum shows that two species, quite differing from 
Harmothoe mibricata, had been confounded together. One is Nychia cirrosa, Pall., and 
the other resembles Polynoe longisetis, Grube [Harmothoe malmgreni. Bay Lankester). 
Polynoella levisetosa, n. gen. and n. sp. (PI. XI. fig. 4; PI. XV. fig. 3; PI. XVI. fig. 4; 
PI. XVIII. fig. 6 ; PL XIX. fig. 8 ; PI. XIa. fig. 7 ; PL XXXIIa. fig. 6). 
Habitat. — A single specimen was trawled at Station 235 (south of Yedo in Japan), 
June4, 1875; lat. 34° 7' N., long. 138° 0' E. ; depth, 565 fathoms ; bottom temperature 
38°'0, surface temperature 73°‘0 ; mud. 
1 Archivf. Naturgesch., xli. p. 82, fide De Quatrefages, &c. 
2 Journ. Linyi. Soc. Land., viii. p. 190. ^ p. 191 . 
^ Aniiel. Chetop. of the Virginian coast {Trans. Albany Inst., vol. i.x., 1879), p. 10, pi. hi. figs. 23-31. 
^ Annel. Fauna d. Philippinen, p. 37. ® Journ. Linn. Soc. Land., viii. p. 161. 
