312 A. H. Clark. 



brouglit to these young colonies on the first ships from Europe, which 

 commonly called at some African port on the way out. If all these ani- 

 mals were successfully brought from Afriea to the West Indies imder the 

 exceedingly trying and unfavourable conditions of ship life in the early 

 years of the seventeenth Century, it is only reasonable to suppose that a 

 much greater exchange of faunas has taken place between north Afriea 

 and Spain in the hundreds of years of constant intercommunication. 



The crinoids of the region of the Strait of Gibraltar are very interesting 

 in the light which they throw upon this question. From Malaga (the loca- 

 lit^" nearest to Gibraltar from which crinoids are known) we have Antedoii 

 mediterranea^ representing an extreme type of the genus, while at Tangier 

 and on the coast of Morocco we lind A. mor^occana, the most extreme 

 species in exactly the opposite direction. 



II. The Crinoid Fauna of The West Coast of Afriea. 



Having thus briefly sketched the relationship between the crinoid 

 fauna of the Atlantic Ocean as a whole and that of the Indo-Pacific region 

 (taken in a broad sense) from which it took its origin at various epochs 

 in the past, and having shown that, so far as the crinoids are concerned, 

 the Atlantic is biologically an Inland sea instead of a true ocean, just as 

 oceanographically and meteurologically it is an inland sea, we now pass to 

 a consideration of the crinoid fauna of the African west coast in detail. 



Only three littoral crinoids are knoAvn to occur on the west coast 

 of Afriea, including the outlying islands. These belong to two widely diffe- 

 rent genera, Antedon^ exclusively Atlantic, included in the suborder Macro- 

 phreata and in the family Atitedonidae, and Tropiomeira, represented in 

 the Atlantic, Indian and Pacific Oceans, included in the suborder Uligo- 

 phreata and in the family Trojnonietridae. 



The Genus Trojno^netrci. 



The genus Tropiometra as a whole has a very extensive ränge, being, 

 in fact, the most widely spread of all the genera of recent littoral crinoids. 



Its species fall naturally into two quite distinct specific groups. One 

 of these, including species of very large size with perfectly smootli arms, 

 is confined to the east, one form (T7'opiornetra afra) occurring in the Au- 

 stralian region and the other (T. macrodiscus) in the waters about southern 

 Japan. 



