79 



separately. First of all, only 34 living species of invertebrate were taken, 

 although 19 stations were occupied (fig. 26). The sampling of this environ- 

 ment was based on six rock dredges, five piston cores (10 cm. diameter), 

 two gravity cores (4 cm. diameter), two box dredges, two shell dredges, 

 one deep diving dredge and one orange peel grab. The living animals were 

 taken by the various dredges, while the unusual shell remains were found 

 in the cores and orange peel. Except for the deep diving dredge (really 

 a trawl), no large-opening samples were taken, which accounts for the lack 

 of large crustaceans which are so important in the other Gulf of California 

 assemblages. Because neither large trawls or grab samples were taken in 

 this environment, there can really be no valid comparison between the 

 other assemblages and this one. What was taken by this gear should be 

 mentioned, nevertheless, as these same devices were used in conjunction 

 with other gear in other parts of the Gulf and did not produce this com- 

 bination of faunas elsewhere. The living faunas are largely epifaunal, 

 since most of the dredges were taken on a rock or gravel bottom. Those 

 living species unique to the northern basins are listed below: 



Hexacorals 



Octocorals 



Dentalium pretiosum berryi 

 Siphonodentalium quadrifis- 

 satum 



1 Stat. 



Stat. 



Asteroids 

 Astropecien ornatissimus 



Stat. 



Another 14 species of invertebrates were also taken alive in this environ- 

 ment, but were also taken at almost the same depths in the central and 

 southern Gulf. None of the species were abundant as to numbers per 

 station. 



The dead shells collected from the basins and troughs are divided into 



