1914] 
Pearse: Fauna of the Rock Beaches 
75 
than in it. Its range of movement is apparently not so limited as that 
of Patella, Fisurella, and Siphonaria (Willcox, ’05). Ten individuals were 
watched from day to day. Only one remained in approximately the same 
spot for more than a week, and it did not maintain a definite orientation. 
Polyneces heros (Adams). Common on sandy beach at Station 4; dead 
shells were also present on the flats at Station 14. This species is active 
at high water but burrows when exposed by the falling tide (fig. 27). 
Crepidula fornicata Lamark. At Station 4 several were observed on 
the shells occupied by Pagurus acadianus, and dead shells were not un- 
common. 
Crepidula plana Say. On Cancer borealis and the shells occupied by 
Pagurus acadianus. 
Littorina litorea (Menke). This was the only animal that was present 
at all stations and in all habitats. On the sand beaches (Station 4) it 
became rather scarce but was abundant in all other places. 
Littorina rudis (Gould). Not very common. Most frequently met near 
high tide mark but occurred in all zones on the rock beaches. 
Littorina palliata (Gould). Rather common among Ascophyllum and 
Fucus on rock beaches. 
Purpura lapillus (Lamark). Abundant under Ascophyllum and below 
on rock beaches. The egg cases (fig. 11) of this species were abundant 
on the rocks under the algae. The snails do not expose themselves like 
Littorina lotorea and L. rudis but usually remain under cover. 
Nassa ohsoleta Stimpson. Common on certain parts of the mud flats at 
Station 14. The egg cases were fastened on eel grass. When left exposed 
at low tide most of these snails burrowed in the mud. 
Mytilus edulis (Limnaeus). Abundant everhwhere except on the sand 
beaches — in little pools above the barnacle zone, in the Chondrus Zone 
(fig. 16), and forming enormous beds on the mud flats. 
Modiola modiolus (Turton). Typically an inhabitant of the'pools in the 
Chondrus Zone. Apparently this species cannot stand exposure to desic- 
cation and variable temperature like Mytilus edulis. Observed at Stations 
1, 2, 5, 6, 7, 8, 9, 10, 12. 
Mactera solidissima Chemnitz. “Dead” shells were common on the 
sandy beach at Station 4. 
Venus mercenaria Linnaeus. Not uncommon near low water mark on the 
sandy beach at Station 4. 
My a arenaria Linnaeus. Abundant near the shore on the mud flats at 
Station 14. 
Ensis americana (Verrill). “Dead” shells on the beach at Stations 4 
and 13. 
Saxicava arctica Deshays. In the Chrondrus Zone near the open ocean. 
Stations 7 and 8. 
Callista convexa Adams. “Dead” Shells on mud beach in eel grass at 
Station 14. 
Tottenia gemma Perkins. Dead shell on sand beach at Station 4. 
