NO. 2 HARTMAN, BARNARD: RENTHIC FAUNA OF DEEP RASINS 231 



SIZE OF ANIMALS IN THE BASIN 



Large animals are not a conspicuous part of the basin samples 

 but there are several reasons to believe that potential large animals 

 have not been adequately sampled. The total frequency of animal 

 specimens in the basins is 56 times less than on the coastal shelf. From 

 our experience with shelf samples we can estimate rather accurately 

 that only 1% of the shelf animals larger than 2 mm are conspicuously 

 large organisms (that is, a worm longer than 20 mm or weighing 

 more than one gram). A total of 3250 animals was collected from 

 all the basin samples, thus providing by shelf comparison a potential 

 total of only 32 conspicuously large basin animals. This is probably 

 close to the total we actually recovered. Among these large organisms 

 were two ghost shrimps, Calastacus quinqueseriatus, Callianassa goni- 

 ophthalma, a large echiuroid Prometor poculutn, another unnamed 

 echiuroid, several large polychaetes, as follows: Onuphis vexillaria, 

 Hyalinoecia tubicola stricta, Ilyphagus ilyvestis, Leanira calcis, L. alba. 

 Clymenopsis cingulata, Asychis lacera, Myriochele pygidialis, Melin- 

 nampharete eoa, Melinnexis moorei, three species of Praxillella and 

 one or two large sipunculids. Florometra perplexa, the crinoid, has 

 been seen in photographs of the bottom. Solemya Vjohnsoni is the only 

 large mollusk to be recovered. 



Because large organisms are widely dispersed, it is probable that 

 a number of large species exist in the basins which we have not re- 

 covered with our sparse sampling, and other motile ones may escape. 

 What is of conspicuous interest is that all of the large animals in 

 the basins are strictly bathyal species except Asychis lacera, which 

 exists on the shallower coastal slopes, as shallow as 75 meters. Not 

 one of the large common shelf species, such as the echiuroid Listriolobus 

 pelodes, the holothurian Molpadia intermedia, or the numerous poly- 

 chaetes in the genera Glycera, Nephtys, the family Maldanidae, 

 Onuphidae, and others, is to be found in the basins. On the other 

 hand, many small-sized shelf species exist in the basins, as seen by 

 Table 3. 



Wherever generic and family comparisons can be made in the 

 Polychaeta from basin to shelf, the bathyal basin species are larger 

 than their phylogenetic shelf equivalents, but where shelf species oc- 

 cupy the basin floors they are smaller, and less well developed in terms 

 of segmental count, gills, pigment and eyes. 



