SEA-URCHINS AND HOLOTHURIANS 289 



Among characteristic deep-sea genera, Homolampas 

 (Fig. 89), Prionechimts, Pourtalesia, Cionobrissiis, and 

 Phormosoma, are all found in Indian waters, Homo- 

 lampas at the great depth of 1644 fathoms, and 

 Prionechinus at the same depth, and also at the 

 greater depth of 1840 fathoms. The only genera of 

 the Indian littoral that are also represented on the 

 abyssal slope are Lovenia, one species of which 

 [Lovenia gregalis, Fig. 88) has been found in abund- 

 ance in 475 fathoms, and Brissopsis, of which one 

 species has been dredged in 609-753 fathoms in the 

 Bay of Bengal. Like their shallow-water kindred, the 

 sea-urchins of the deep sea are, as a rule, remarkable 

 for the scrupulous cleanness of their outside, but the 

 great spines of the bathybial Cidarids are often 

 encrusted with barnacles and sponge. 



The HoLOTHURiANS of the Indian abysses are for 

 the most part absolutely different from those of the 

 off-shore waters. Most of them belong to Theel's 

 Order Elasipoday an order ''which cannot be derived 

 from the present shallow-water fauna, but must have 

 originated from a past type that certainly bore an- 

 other stamp." A few belong to the apodous family 

 MolpadidcB. 



The Elasipoda, which are purely abyssal forms, 



are strangely unlike the familiar sea-cucumbers of the 



reefs, for not only have they become profoundly modi- 



T 



