[371] INVERTEBRATE ANIMALS OF VINEYARD SOUND, ETC. 77 



on muddy shores, burrowing beneath, the surface, at or just below low- 

 water mark. 



Many of the Annelids found on muddy shores occur also on sandy 

 shores, especially where there is a mixture of mud with the sand, and 

 consequently they have been mentioned in the preceding pages. 

 Among these are Nereis virens (p. 317, Plate XI, figs. 47-50) and N. 

 linibata, (p. 318, Plate XI, fig. 51,) both of which are common on muddy 

 shores ; also Diopatra cuprea, (p. 320, Plate XIII, figs. 67 and 68 ;) Lum. 

 briconereis opalina, (p. 342, Plate XIII, figs. 69, 70;) L. tennis, (p. 342;) 

 Maldane elongata, (p. 343;) Notomastus luridus, (p. 342;) Notomastus fili- 

 formis, (p. 342;) Cirratulus grandis, (p. 319, Plate XV, figs. 80, 81;) Cis. 

 tenides Gouldii, (p. 323, Plate XVII, figs. 87, 87;) all of which are 

 found both in mud and sand, but prefer, perhaps, a mixture of the two. 

 Rhynchobolus Amcricanus (p. 342, Plate X, figs. 45, 46) and R. dibran- 

 cliiatus (p. 341, Plate X, figs. 43, 44) are also found in mud, though per 

 haps more common in fine sand, or sandy mud. 



The &quot; blood-drop,&quot; Polycirrus eximius, (p. 320, Plate XVI, fig. 85) is 

 however, a species that belongs properly to muddy localities, and it de 

 lights in the softest and stickiest mud of the shores, near low- water 

 mark. The larger blood-drop, Clicctobranclim sanguineus, (p. 320,) is also 

 found in similar situations, and the soft inucl, filled with decaying veg 

 etable matter, seems to be its most congenial home. 



Of Mollusks there are comparatively few species that are peculiar to 

 muddy shores, but there are many that live almost equally well in such 

 localities and on shores or bottoms of other kinds. 



Among the Gastropods, the proper mud-dwelling species are few. 

 The Ilyanassa obsoleta (p. 354, Plate XXI, fig. 113) is the most abund 

 ant, for it occurs everywhere over the mud-flats in great numbers, ancl ? 

 in cold weather, often crowds in large numbers into the pools left on 

 the flats. The Nassa vibex (Plate XXI, fig. 114) has nearly the same 

 habits, but is comparatively rare. It is more frequently found among 

 the eel-grass, and is more common farther south. 



The Eupleura caudata (Plate XXI, fig. 117) is usually found rather 

 sparingly in this region, but in one locality, at Waquoit, it occurred in 

 considerable numbers in the small streams and ditches in the muddy 

 marshes near the shore. It occurs occasionally at low-water, but is 

 more often met with on muddy and shelly bottoms in the shallow water 

 of the bays and sounds, and is much more common farther south. The 

 Crepidula convcxa (p. 355, Plate XXIII, fig, 128) is very common on 

 the shells of Ilyanassa obsoleta, especially when they are inhabited by 

 &quot; hermit-crabs.&quot; It is also frequently found on the eel-grass, where, in 

 August, it often deposits its bright yellow eggs inclosed in small, gela 

 tinous masses, which are grouped in clusters. 



The Bulla solitaria (Plate XXV, fig. 161) is a species restricted to 

 muddy shores and bottoms, in sheltered situations, and is found also in 

 muddy ponds and estuaries. The color of the animal of this species is 



