VoL. 2] Ritter.—The Pelagic Tuncata. 71 
and most of all over the nucleus. Whole surface, except for a 
broad area at the anterior end, beset with low, spine like processes. 
Frequently a girdle of indefinite limitation of dark green in the 
mid body, across the dorsal side and extending well down toward 
the mid-ventral line, the color, which is on the surface of the 
test, being densest laterally. The edges of the posterior append- 
ages densely and uniformly colored with the same green. Body 
muscle bands 20, occasionally 19 or even 18, uniformly spaced 
and mostly all parallel, but the first and second inclined some- 
what backward on the dorsum. All (in old zooids only?) limited 
to the dorsal half of the body, and all interrupted in the mid- 
dorsal line, and typically, the 7th or 8th or 9th interrupted 
laterally. A single broad band in dorsal lip broadly interrupted 
on each side of median line; also a pair of short, longitudinal, 
nearly parallel, widely separated bands in this lip; two bands 
in ventral lip; a complicated and variable crossing of short 
bands at angle of orifice. Nine or ten or more delicate, wavy, 
more or less interrupted bands belonging to the atrial siphon. 
Endostyle slender, gently curved to conform to the outline of 
the body, reaching entirely back to the nucleus. Guill relatively 
rather short, extending from a little in front of the first muscle 
band to the nucleus. Hyphysis close to anterior end of gill, but 
short distance in front of ganglion, forming a distinctly pendant 
tuberele, on which the rather large, irregularly triangular mouth 
mouth is situated. 
Fig. 17.—Costata-tilesii, aggregate generaion. 
(b) Aggregate (sexual) generation.—F ig. 17. Body in gen- 
eral cylindrical, but irregular, especially posteriorly from the 
