50 REPORT OF COMMISSIONER OF FISH AND FISHERIES. [344] 



of the twenty-fourth body-segment an appendage develops below the 

 lower fascicles of seta3, and farther back becomes broad, foliaceous, and 

 divided into several lobes; back of the twenty-eighth segment the 

 branchiae appear in a row on each side of the back, and soon become 

 long and ligulate; at the same time other ligulate appendages develop 

 from the upper lateral appendages, which become dorsal, and these, 

 with the gills, form four rows of processes along the back, 'outside of 

 which are the elongated set3 and other appendages. The posterior 

 part of the body is more slender and much more delicate than the an- 

 terior part, and so fragile that an entire specimen can rarely be obtained? 

 and those that are obtained, when in confinement very soon detach 

 fragment after fragment, until only the anterior part is left. In their 

 natural habitations they would undoubtedly be able to reproduce their 

 lost parts, like many other annelids. The color of this worm is ocher- 

 yellow, tinged with orange, or dark orange ; there are usually two rows 

 of dark-brown spots along the back ; the branchiae are blood-red ; and 

 posteriorly there is a brownish red median dorsal line. The proboscis 

 is very singular, for it is divided into several long, flat, digitate pro- 

 cesses, separate nearly to the base, and somewhat enlarged at the end. 



Another species of this genus, of smaller size, A. fragile Y., often oc- 

 curs in the sandy flats in great numbers, its small holes sometimes com- 

 pletely filling the sand over considerable areas and extending nearly 

 up to half- tide mark. This species grows to the length of four inches 

 or more, with a diameter of about .10. Its head is even more acute 

 than in the last species, with a very slender, translucent apex. The 

 body has the same form, but is more slender. The processes above and 

 below the fascicles of setae begin to appear at the fourteenth segment, 

 and the setae begin to be decidedly elongated at the fifteenth. The 

 dorsal branchiae begin on the sixteenth segment, and become long and 

 ligulate at the twentieth. The color is yellowish orange to orange-brown ; 

 the dorsal surface, posteriorly, and the branchiae are red. The body 

 posteriorly is very slender and extremely fragile. The last or caudal 

 segment is smooth, oblong, with two long filiform cirri at the end. The 

 proboscis is large and broad, consisting of numerous, often convoluted, 

 lobes or folds, united by a thinner membrane or broad web. 



The Aricia ornata Y. is another related species, living in similar 

 places with the last and having similar habits. The head is acute in 

 this species, but the dorsal branchiae and lateral appendages com- 

 mence much nearer the head, and the side appendages are developed 

 into crest-like, transverse series of papillae, which cover the lateral and 

 ventral surfaces of the body anteriorly. 



Two species of Spio also occur in similar situations inhabiting small 

 round tubes or holes made in the sand near low-water, often occuriug 

 in great numbers in certain spots. They prefer localities that are not 

 exposed to the full force of the storms. One of these, 8. setosa Y. (Plate 

 XIY, fig. 77,) is remarkable for the length of the setse in the dorsal 



