8 W. G. RIDEWOOD. 
anteriorly into paired plumes which are usually provided with paired pinnules, and 
produced postero-ventrally into a post-oral lamella. Trunk large, with distinct 
division of the coelom, not opening to exterior, and primarily paired. A stolon for 
the production of buds projects from the ventral side of the trunk region of the 
body. Alimentary canal bent, mouth posterior to the pedicle of the shield, a 
notochordal outgrowth from the front of the pharynx, gill-slits leading from the 
pharyngeal cavity to the side of the body, anus antero-dorsal, near the bases of 
the plumes. Gonads simple, one pair, with short ducts opening near the anus. 
Sub-genus Demiothecia, Cavity of the tubarium continuous, and all ostia leading 
into that cavity. 
Text-Fiaure 4.—Cephalodiscus dodecalophus. A, — portion of tubarium cut lengthwise; B, — portion of 
tubarium cut transversely, The polypides are not shown. The cavity is continuous, irregular, and with 
several ostia (x 3). 
Species dodecalophus. Material. Obtained by H.M.S. ‘Challenger, in 1876, 
in the Straits of Magellan, Station 311; depth, 245 fathoms; bottom, blue 
mud, Described by M’Intosh in Ann. Mag. Nat. Hist. (17) and in the Report 
of the ‘Challenger’ Expedition (19). Tubarium. Colony irregularly branched, 
and straggling, some of the branches fusing up to form a network, the cross-bars 
being usually solid. Colony reaching a length of at least 225 mm.; distance 
between one branch or cross connection and the next about 22mm.; width 
of branch, 4 to 6 mm., not including spines ; cavity of tubarium partially divided 
up by bars, ridges, and incomplete partitions (text-fig. 4), ostia numerous, 
irregularly placed, oval, 1°5 by +7 mm., sessile, i¢., without peristomial tubes, 
