430 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
verse diameter. Even more striking, although not always percep¬ 
tible to the naked eye, is the variable character of the branchiae, 
which are in some specimens dichotomously branched, and in others 
entirely unbranched. 
The coloration of the branchiae shows two distinct phases—• pur¬ 
ple or wine-color and whitish or tawny. Either color may be present 
to the exclusion of the other, or the two may be in alternate,, trans¬ 
verse bands. The eye-spots may be few or many, but I have found 
'.no specimen without them. Although a lens is absent, the eye-spot 
produces a wart-like elevation of the cuticula which covers it (Fig. 
184). The eye-spots are of various sizes, the largest being over 
;twice the diameter of the smallest. They are scattered at irregular 
intervals along the rachis, but are more numerous towards the base 
than towards the tip. None are found near the tip and very rarely 
anv on the branches. 
The tube is adhesive, and is usually affixed by its lower extremity 
or by its side to a stone or pile. At Pacific Grove the species attains 
a large size and is abundant on rocky bottoms from low-water mark 
to a depth of several fathoms. 
Megachone gen. nov. 
Form terete; no ventral shields; collarette flaring, interrupted 
only at ventral notch ; branchiae connected by a web; no spatulate 
thoracic setae; thoracic uncini with long manubrium, of one kind 
only; abdominal uncini short avicular plates; no ventral fissure at 
posterior end. 
48. Megachone aurantiaca sp. nov. PI. 18, figs. 186-192. 
Form subcylindrical, spiral in contraction, thickest in posterior 
portion; anterior end truncated; collarette broad (Figs. 186, 187) ; 
body narrowed in region of thorax and enlarged in abdomen; pos¬ 
terior extremity abruptly tapered to a minute tip, which is curved 
dorsad ; anus terminal. Somites 75 in number. 
Branchiae 20 on each side, unbranched (Figs. 187, 188), closely 
appressed, tips pointing ventrad ; radioles invisible until branchiae 
are raised. 
Thorax (Fig. 186) of eight somites; peristomium, with collarette, 
one and one half times the length of the other thoracic somites; 
bears a small tuft of setae, but no uncini; a slight indication of two 
rings; the biannulate condition more strongly marked in the other 
thoracic and abdominal somites. 
Fecal groove extending forward along mid-dorsal line to ninth 
