284 THE VOYAGE OF H.M.S. CHALLENGER. 



Placogorgia, Wright and Studer. 



The only sjiecies of this genus {Placogorgia atlantica) occupies a quite isolated position 

 off St. Paul's Rocks, in the Atlantic. 



Acamptogorgia, Wright and Studer. 



Both the species found by the Challenger, Acamptogorgia arhtiscula (Gray) and 

 Acamptogorgia alternans, are from the Pacific Oceaia, Japan and Fiji ; if the species 

 described by Koch ' as Muricea behrycoides, n. sp., belongs to this genus, then its 

 geographical area must be extended to the Mediterranean. 



Echinogorgia, Kolliker. 



All the species of this genus belong to the Indo-Pacific Ocean, Echinogorgia sassapo 

 (Esp.) at the Mauritius, Echinogorgia furfuracea (Esp.), Echinogorgia cerea (Esp.), 

 Echinogorgia canceUata (Verr.), and Echinogorgia intermedia, Std., off North-west 

 Australia, Echinogorgia, pseudosassapo, KoL, at Torres Strait, Echinogorgia ramulosa 

 (Gray), at the Philippines, while Echinogorgia flahellum (Esp.) and Echinogorgia 

 umbratica (Esp.) have as localities the "East Indies." Echinogorgia auranticoca 

 (M.-Edw.) has been found off Callao. 



Thesea, Duchassaing and Michelotti. 



o 



Thesea guadalupensis, D. and M., is recorded from Guadeloupe; Thesea gemmata, 

 Verrill, was obtained from deep water at St. Croix, in the West Indies. 



Acis, Duchassaing and Michelotti. 



Of the three species of this remarkable genus, one, Acis guadalupensis, D. and M., 

 was found off Guadeloupe, a second, Acis orientalis, Rid., at the Mauritius, while the 

 third, Acis pustidata, was found by the Challenger at Japan. 



Muricella, Verrill. 



The central area for the species of this genus would seem to be the East Indies ; 

 Muricella humosa (Esp.), Muricella tuberculata (Esp.), have not been rediscovered, and 



' Fauna und Flora des Golfes von Neapel, xv. p. 52. 



