72 GUIDE TO LOCALITIES. 



carried up from mussel-beds off shore, the latter commonly brought 

 from deeper water, held firmly in the roots of the Laminaria. The 

 latter species is often very large and robust, and frequently shows 

 deformations caused by obstructions during growth. The plicated 

 Modiola plicatula is much less common on the sand beaches, but 

 may be found always among the marsh grass near the mouth of 

 fresh-water streams. 



Several other species of molluscs occur among the roots of the 

 Laminaria, in addition to a number of other deeper-water ani- 

 mals. The shells most frequently found are Anomia aculeata and 

 Saxicava arctica. Among the larger shells occasionally thrown on 

 to our beaches are Petricola pholadiformis, readily recognized by its 

 plicated anterior end ; Astarte castanea, known by its smooth chest- 

 nut-brown epidermis ; and Cytherea convexa, a shell very similar to 

 Venus mercenaria of the south coast, but differing in its chalky 

 white color, smooth surface, and more rotund form. Venus mer- 

 cenaria has been found, but rarely. Macoma fusca, a thin, white, 

 transversely subovate shell, with a dusky epidermis, occurs on this 

 and other sand beaches. Its habitat is shallow still water, with a 

 muddy bottom. 



Among the small shells found. in great abundance on our beaches, 

 Tellina tenera and Tottenia gemma are exceedingly common. The 

 former, a tenuous semi-translucent shell with short pointed poste- 

 rior end, often more or less colored, and of a pearly lustre, is 

 usually the most abundant. Single valves and shells with the two 

 valves united are found almost everywhere on the surface of the 

 sand. Many of these show a hole bored by some carnivorous gas- 

 tropod. The animal is found sometimes on the beach, but its 

 habitat is probably in the fine sand just below low water. Tottenia 

 gemma may be recognized by the amethystine color of its umbonal 

 region. It is a very pretty little shell, and early attracted atten- 

 tion, according to Gould having been sent to England as one of 

 the natural curiosities of this coast. Its small size causes it to be 

 overlooked, unless the method of collecting suggested for the small 

 gastropods be employed. It is thought commonly to be the fry of 

 Venus mercenaria on account of its. purple beak (Gould) . With 

 these species are found many young specimens of Mya, Mactra, 

 Mytilus, Modiola, etc. Mya arenaria, Mya truncata and Pecten 

 tenuicostatus also occur ; the first in abundance, the second rare. 



Next to molluscs, crustaceans and worms are the most abund- 



