Figure 8. — Asymmetric ripple marks on the sea bottom at station 44. Direction of view is northeast, and the water 

 current that formed the ripples flowed toward the northwest. Identifiable animals: A. burrowing sea anemone; 

 B. hermit crab. Scale bar is 10 cm. long. 



recently, grab-type bottom samplers and 

 photography have been used successfully 

 (Vevers, 1952; Mclntyre, 1956; Emery, Merrill, 

 and Trumbull, 1965; Wigley and Emery, 1967; 

 and others). From results of the above- 

 mentioned studies, the photographic method 

 appears promising for many purposes, even 

 through it may also be the most inadequate 

 for identifying the animals and determining 

 their exact size. 



Our results substantiate conclusions from 

 other studies that revealed that photographic 

 techniques are superior to dredging methods 

 for obtaining quantitative measures of the 

 large epibenthic species and determining local 

 distribution (dispersion) of animals and sedi- 

 ment features. Estimates of density of 

 epibenthic invertebrates derived from bottom 

 photographs and from scallop-dredge samples 

 at the four stations (fig. 1) off Massachusetts 

 are listed in table 2. Densities based on an 

 analysis of photographs were substantially 

 higher than those based on dredge collections. 

 This difference held true for every taxonomic 

 group (as well as for all taxonomic groups 

 combined) except the Porifera and Annelida. 



Only a few Porifera and Annelida were col- 

 lected in the dredge hauls; none was observed 

 in the photographs. 



Species compositions of animals at the 

 Georges Bank stations (42, 44, and 45) were 

 generally similar but differed markedly from 

 the fauna south of Martha's Vineyard (station 5). 

 On Georges Bank the dominant species were: 

 Echinarachnius parma , Strongylocentrotus 

 drobachiensis , Buccinum undatum , Colus 

 stimpsoni , Neptunea decemcostata , Arctica 

 islandica , Placopecten magellanicus , and 

 Pagurus acadianus . Principal species south of 

 Martha's Vineyard (station 5) were: Asterias 

 vulgaris , Leptasterias tenera, and Cancer 

 borealis . 



Echinoderms were, by far, the most abund- 

 ant major taxonomic group sampled. Echinoids, 

 a principal subgroup, were represented chiefly 

 by the sand dollar and the green sea urchin. 

 Sand dollars were particularly numerous (6.7 

 per square meter) at 82 m. on Georges Bank 

 (station 45). They were less common at 

 shallower depths on Georges Bank (stations 42 

 and 44) and were absent at 59 m. south of 

 Martha's Vineyard (station 5). Asteroids were 



10 



