174 BULLETIN OF THE 
fourth the circumference of the body, lies midway between anterior and pos- 
terior border. Five similar lateral lines of black pigment alternating with 
those of the dorsal region are found on the sides of the larva. These markings 
are placed in two lines, and are found on each segment, but do not join the 
dorsal series of markings, since they are placed in different regions of the body 
segments, which are not continuous. On the ventral side of the larva, similar 
lines of black pigment also appear ; but, instead of extending across the medial 
fine, as the markings on the back, they are arranged in two series of parallel 
markings, of which there 1s a row on either side of the median line. 
The number of segments in the next oldest larva has increased to seven, or, 
if we include the terminal, to eight. The pattern of color in each segment is 
the same as that in the younger larva already described. In this, the number 
of pigment spots on the head has also increased. At the base of the cephalic 
appendages, near their origin under the ciliated ridge, more especially in the 
ear-like protuberances (“auricles”) which carry the embryonic sete, there 
will also be noticed prominent patches of crimson pigment. 
Spines indicating the position of future parapodia have appeared in the body 
segments, although the lateral protuberances are still quite small. The spines 
of the penultimate segments in many specimens are much longer than the 
others. The intestinal tract, with the exception of the bend which the @soph- 
agus makes just before it opens into the stomach, follows an almost direct 
course from the mouth to the vent. The lips and walls of the esophagus are 
richly ciliated. The external walls of the body are sparsely covered with 
small black pigment dots. 
Aricidea sp. (7). 
Plates Il. and VI, 
A series of larval Annelides referred to the genus Spio has been described by 
Claparéde and Metschnikoff.* The youngest larva, which is here considered 
the young of Aricidea,} closely resembles the oldest which they describe. 
The youngest larva of this genus has a close likeness to the young Spio (p. 
173), but differs from it in having three pairs of sete, one upon the head, a 
second on the body at about two thirds the distance from the mouth to the 
posterior end of the body, and a third at or near the posterior terminal segment. 
In very young larvee these spines are very short. The head is more rounded 
than that of Spio, but like it has two ear-like lappets from which the tempo- 
rary bristles below the ring of cilia arise. - There are no eye-spots, and instead 
of well-bounded ocelli irregular patches of pigment are found on the dorsal 
surface of the head in a position where eye-spots are later to be seen. 
The temporary head bristles are smooth, and destitute of the lateral spurs 
* Zeit. Wiss. Zool., XIX., 1869. 
+ Aricidea Webster is not found in our waters. It was taken by H. E. Webster 
on the Virginian coast. Trans. Albany Inst., Vol. IX., 1879. 
