606 F. H. GRAVELY. 
Claparéde’s eleven-segment larva the posterior sezments are 
perhaps insufficiently developed to show the dorsal lobe in 
any case. 
McIntosh (1908, pp. 112-3, text-fig. 45) briefly describes a 
minute pelagic worm, about one eighth of an inch long, in 
which “every foot from the second to the last is furnished 
with a very long translucent tuft of swimming-bristles.” 
Only a single specimen of this worm is known, and its precise 
position is uncertain, but McIntosh states that it seems to be 
most nearly related to the Syllide and Alciopide. 
EXTERNAL Features oF THE Heap AND ANTERIOR SEGMENTS 
IN LARV#® OF THE SPIONIDZE AND POLYDORIDA. 
In the Nectosoma larvee of the Spionidee and Polydoride 
there is a capacious ‘‘ mouth” bordered by a pair of large 
lateral lips. These structures appear to be quite character- 
istic of the two families, and to have caused in them 
considerable modifications of the ciliation of the anterior seg- 
ments. ‘lhey have been briefly referred to by Claparéde and 
are indicated in his figures of the larva of Polydora Bose., 
(= Leucodora, Johnst.) and in his figures of Spionid larvee 
(1863, Pl. VI, figs. 1 and 3; Pl. VIL, figs. 1, 6, and 7), amdam 
Cunningham and Ramage’s figure (1887, Pl. XX XVII, fig. 2/7) 
of an advanced larva referred by them to Nerine cirratulus 
they are very conspicuous. No full account of them has as yet 
been published, however, and many authors appear to have 
overlooked or ignored them altogether, in spite of their great 
importance in the morphology of these larve. 
In the following descriptions the species of the various 
larvee referred to are indicated by the letters used for that 
purpose in my systematic description of them (Gravely, 1909). 
Spionid A (“Claparéde’s Unknown Larva of Spio,” 
McIntosh, 1894). 
This larva may serve as a general type, and so will be des- 
cribed in more detail than the rest. It was originally 
