INVERTEBRATE ANIMALS OF VINEYARD SOUND, ETC. 345 



bundles ; tbe two large tentacles (of whicli only one is dra^Yn in the 

 fignie) are usually folded backward between the red dorsal branchiae, 

 which form a row along the back on each side. The other, aS'. robusta 

 Y., is a stouter species, which has much shorter setae in the dorsal fasci- 

 cles; the middle lobe of the head is emarginate in front and the lateral 

 lobes are convex. Both species have four small eyes on the top of the 

 head, those of the posterior pair nearest together. In similar i^laces, 

 and often associated with the two preceding species, another allied 

 worm often occurs in great abundance, completely filling the sand, in 

 its chosen abodes, with its round vertical holes, and throwing out cylin- 

 ders of mud. It is so gregarious that in certain spots hundreds may be 

 found within a square foot, but yet a few yards away, on the same kind 

 of ground, none whatever may be found. This is Scolecolepis virldis 

 Y. This species, like the two preceeding, has a pair of large tentacles 

 on the back part of the head, which are usually recurved over the back 

 between the rows of ligulate branchiae, and four eyes on the top of the 

 head ; the central lobe of the head is slightly bilobed in front, the lateral 

 ones convex; the branchiae are long, slender, ligulate, meeting over the 

 back, and exist only on about one hundred segments, or on about the 

 anterior third part of the body. The body is rather slender, depressed, 

 and about three inches long when full grown. The color is usually dark 

 green, or olive-green, but sometimes light green, or tinged with reddish, 

 anteriorly ; the brancliiae are bright red; the large tentacles are light 

 green, usually with a row of black dots, and often crossed by narrow 

 flake-white lines or rings. This species has been found abundantly on 

 Naushon Island, and other localities in that region; at New Haven ; and 

 at Somer's Point and Beesley's Point, New Jersey. With the last species 

 at Great Egg Harbor, New Jersey, another more slender species of the 

 same genus occurred, Scolecolepis tenuis Y. This was three or four 

 inches loug and very slender; the body was pale green; the tentacles 

 longer and more slender than in the last, whitish, with a red central 

 line ; the branchiae red, often tinged with green, shorter than in the last. 

 The head is relatively broad, with the central lobe rounded iu front. 

 The branchia) are confined to the anterior part of the body. The setae 

 ill the upper fascicles are much longer than in the last species, those of 

 the three anterior segments longer than the others and forming fan- 

 shaped fascicles, directed upward and somewhat forward. 



Another singular Annelid, belonging to the same tribe and having 

 nearly the same habits, is represented in Plate XIY, fig. 78, this has 

 been found by Mr. A. Agassiz burrowing in sandy mud at about half- 

 tide, both at Naushon Island and at Nahant, Massachusetts, and he has 

 also described its development and metamorphoses, but I have not met 

 with the adult myself in this region, although the young were frequently 

 taken in the towing-nets in the evening. Mr. Agassiz regards it as 

 perhaps identical with Polydora ciliatum of Europe. It occurred in 

 large colonies, closely crowded together, building upright tubes in the 



