168 PROCEEDINGS OF THE ACADEMY OF [Jan., 



Protula geniculata sp. nov. (PI. XI, figs. 17, IS; PI. XII, fig. 38.) 



The tAvo specimens upon which this species is founded were taken 

 from the tubes, and are consequent!}^ in a rather poor state of preserva- 

 tion and altered in shape by the constraint. Except for the flattened 

 and tapering caudal end the form is completely terete and the thoracic 

 membrane is wrapped closely about the body. Following are the 

 measurements of the type : Total length, 27 mm. ; branchite, 5 mm. ; 

 thorax, 5.5 mm., and diameter of thorax, 1.2 mm. 



Branchiae remain in the type specimen only, and are so fragile that 

 a complete study is impossible. Their bases are short and simple, 

 concealed by the collar ventrally but exposed dorsally. The radioles 

 number about 18 on each side, arise strictly in one row, although in 

 the retracted condition some of the dorsalmost ones are turned inward 

 and spirally twisted, so that they appear partly in a double row. Most 

 of the radioles are rounded in section, Init the dorsalmost one on each 

 side is flattened. There is no basal web. At the base of the radioles 

 the barbs are as long as one-half of the diameter of the thorax, but 

 become gradually shorter toward the tip, where they leave naked a 

 filamentous portion of the radiole about as long as the basal barbs. 

 There is no operculum. 



The strictly ventral collar is produced directly forward to a length 

 about equal to an anterior thoracic somite ; the margin is smooth and 

 entirely without trace of any folds or incisions and with short rounded 

 lateral lobes. The thoracic membrane is rather prominent and pro- 

 duced anteriorly beyond the collar, but not overlapping its lateral 

 lobes. Dorsally the two sides overlap considerably in the middle line, 

 and are thrown into deep oblique folds at each somite, owing to the 

 stowing of a large surface within the small space of the tube. Posteri- 

 orly they reach beyond the last thoracic somite and join in a closely 

 appressed ventral fold covering the first abdominal somite below. 



There are sev'en setigerous thoracic somites and seventy abdominal 

 somites. The bundles of thoracic seta are all at the same level and of 

 similar size; the uncinigerous tori are short, equal and widely separated 

 ventrally on all somites. The sides of the thoracic somites between 

 them are transversely wrinkled. On the abdominal region the anterior 

 tori are nearer the dorsal than the ventral side, but posteriorly they are 

 strictly lateral. At the posterior end the body is beveled toward the 

 dorsal side and is provided with low lateral ridges, but no distinct 

 caudal membrane. Dorsally this flattened region bears a narrow but 

 thick shield plate which tapers to an acute point anteriorly and is 

 partly metameric. It occupies about 20 somites and is white and 



