296 TEE ATLANTIC. [chap, v. 



are mostly simple and solitary, and the greater number belong 

 to the Turbinolidae : nearly all the genera pass back to Tertiary, 

 and a few to Mesozoic times. Upon the whole, the corals must 

 undoubtedly be regarded as affording evidence of a certain re- 

 lation between the deep-sea fauna of the present day and the 

 fauna of shallower water during the deposition of at all events 

 some portions of the Tertiary series. 



Attached Alcyonarians, and especially genera allied to 3£op- 

 sea and Prhnnoa, are extremely abundant in the cooler seas at 

 depths from 500 to 1000 fathoms, sometimes occurring in such 

 quantity as to hamper and clog the trawl, and affording charm- 

 ing exhibitions of elegance of form and beauty of coloring. 

 Certain forms of the Pennatulidse go down to great depths: 

 the genus ZTnibellula, which we at first regarded as of extreme 

 rarity, turned uj) every now and then, usually in nearly the 

 deepest hauls, represented by two or three nearly allied sj^ecies. 



Among the Echinodermata the stalked crinoids of the deep- 

 sea fauna are most interesting, but they are comparatively few 

 in number. The large forms belonging to the Pentacrinidae, 

 although they are very local, appear to be more common than 

 has been hitherto supposed at depths of from three to five hun- 

 dred fathoms. Five or six new species have been added to the 

 meagre list, but most of these are from the South-western Pa- 

 cific, and do not enter into the Atlantic fauna. The Apiocrini- 

 dae, represented by the genera Hhizocrijius, Bathycrinus, and 

 Ilyocriniis, which are of so great interest as the last survivors 

 of a large and important order, are rare prizes at much greater 

 depths. Eepresentatives of all the three genera were dredged 

 in deep water in the South Atlantic. 



Ophiuridea, many of them referable with the common sand 

 brittle-star to the genus Ophioglypha, and many others to the 

 closely allied genus OpMoinimum., came up from the greatest 

 depths, and, particularly in the iSTorth Atlantic, formed a prom- 

 inent feature in the fauna. Asteridea, principally represented 



