COMMUNITIES OF THE SEA BOTTOM 



343 



gastropods and the annelids occur in greater abundance in this than 

 in the Venus-Echinocardium association. In addition to fishes char- 

 acterizing the biome in general, Blegvad (1916) mentions the whiting 

 and dragnet. The aggregation described by Davis appears to belong 

 in this association (Fig. SO). 



1°30'E 2°00'E 2°30'E 3°00'E 3°30'E 4°20'E 



Fig. 80. — Spisula subtruncata consociations. The oldest areas are solid black; 

 those of medium age, shaded; and the youngest, unshaded. The stippling of 

 areas outside the patches is purely diagrammatic. Each dot represents a large 

 number of individuals of Spisula outside the aggregations because Davis gives 

 only frequency and not spatial relations. (After Davis, 1923.) 



Brissopsis-Amphiura-Ophiura Ecotone. Sparck (1935) states that 

 Brissopsis-Amphiura chiajei (BCh.) and Brissopsis-Ophiura {Ophio- 

 glypha)* sarsi community appear to represent a transition which (in 



* Changes in generic names which involve the naming or other designation of 

 communities or their predominant species in the North Atlantic and adjacent 

 waters are as follows: 



Abra becomes Syndosmya 



This changes the designation of Petersen's Abra community (Abra with 

 Echinocardium ; b(abc E) and renames the constituents of others. 



Ophioglypha becomes Ophiura 

 This involves changing Petersen's Brissopsis-(Ophioglypha) sarsii designation 

 as noted above. 



AxiiiuJi becomes Thyasira 

 Thyasini flexuosa is a common or abundant constituent of two communities 

 which may be united as a biome (see Fig. 84, p. 349). 



Maclm becomes Spisula 

 The species subtruncata is prominent because of the very dense aggregations 

 in the North Sea (Fig. 80). 



