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. 



B 



TEXT-FIGTOE 4. Cephalodiscus dodecalophus. A, portion of tubarium cut lengthwise; B, portion of 

 tubarium out 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 22 mm. ; width 

 of branch, 4 to 6mm., 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.e., without peristomial tubes, 



