A. H. CLARK : THE CRINOIDS OF THE INDIAN OCEAN. 5 



completed his work upon those collected by the Dutch steamship " Siboga " i n 

 the Dutch East Indies and among the Piiilippines, including a new species of 

 E ndoxocrinus ^ several of Mclacriii.its, and numerous forms belonging to the Bour- 

 gueticrinidas , heretofore known as inhabitants of the region only from the some- 

 what vague reference of Korotneff. 



2. COMPOSITION OF THE EAST INDIAN CRINOID 



FAUNA. 



The great East Indian region, with its immediate zoogeographic dependencies, 

 is now known to support nearly 400 species of recent orinoids of which about 350 

 are comatulids and about 50 stalked forms. These are distributed among 82 

 genera, of which 69 include comatulids and 13 stalked species. These genera are 

 grouped into 19 families, 14 among the comatulids, and 5 to receive stalked 

 species. 



All of the species are peculiar to the region ; of the comatulid genera 1 1 are 

 found also in the Atlantic while 14 others have close allies in that ocean, making 

 25 in all represented there, and leaving 44 peculiar to, and characteristic of, the 

 East Indian region ; of the stalked genera five are found also in the Atlantic while 

 two have close allies there, giving a total of seven represented in that ocean, and 

 leaving six peculiar to, and characteristic of, the East Indian region. Taking the 

 grouj] as a whole we find that 16 of the genera occur in the Atlantic as well as in 

 the East Indian region, while of the remainder 16 are represented by closely-allied 

 forms, leaving 50, or nearly two-thirds, as peculiar to, and characteristic of, the 

 East Indian region. Among the families of comatulids eight are found outside of 

 the East Indian region while six, and one of the subfamilies of the Comasteridae, 

 are exclusively confined to it, while among the families of the stalked forms the 

 numbers are three and two respectively. As a total we find 11 families out of tlie 

 19 represented also in the Atlantic while eight are confined to, and characteristic 

 of, the East Indian region. 



The preceding analysis graphically brings out the surpassing richness of the 

 East Indian faunal region, but at the .same time it somewhat curiously conceals 

 the wealth of the other regions of the world. No families nor subfamilies are 

 known which are not represented in the East Indies, excepting only the Holopidse 

 which includes the single genus Holopus, but in certain cases the East Indian 

 representation falls far below that in other areas, botli in regard to genera and to 

 species. All the genera of the Atlantic, Antarctic, and Arctic Oceans are closely 

 related to East India genera from which they were evidently derived in the remote 

 past ; but in many cases a .single East Indian genus has apparently given rise to two 

 or more Atlantic genera, all nearly equally related to the parent stock. For instance 

 in the Antedonida? among the Heliometrinse we find the genus Cijdomvtra in the 

 East Indies, and Solanomelva and ProinachocriuHS (derived from it) in the Antarctic ; 

 and also the genus Trichometra, represented both by other species of Trichometra 



