AGI 



Notes on some Stylasterina 

 IN THE Muséum d'Histoire Naturelle de Paris, 



BY Professor s. J. Hickson, Manchester. 



By the kindness of Prof. Joubin, to whom I wisli to express my 

 warmest thanks , I hâve been allowed to examine in Manchester a collec- 

 tion of Stylasterina belonging to the Muséum d'Histoire naturelle. 



The following species are represented : 



Stylaster tiliatus h. and E. — 296 mètres La Praya, and ayS-iSo 

 Cape Verde Islands. 



Errina aspera Linn. — 633 and 898 M. Cape Verde. 



Errina antarctica Gray. — Cape Horn. 



Errina Dabneyi Pourt. — 56 M. Azores, 56o M. Payai, 56o M. Sar- 

 gasses. 



Errina atlantica, nov. sp. — 998-900 M. Azores, 358 M. S. du 

 Payai. 



Pliobothrus symmetricus Pourtalès. — 56 M. Azores. 



Pliobothrus turulatus Pourtalès. — 56 M. Azores. 



Stylaster tiliatus Hickson and England. 



The type spécimens of this species were found by the Siboga expédition 

 in 275 mètres of water olT the Sulu Islands in the Malay Archipelago. 

 The Talisman spécimens were found in 278 mètres off La Praya and 

 2 05-1 5o mètres off the Cape Verde Islands. The occurrence of the same 

 species in two localities so far apart, is a feature of some interest. In such 

 a genus as Stylaster, however, there is a great deai of difficulty in the 

 détermination of spécifie distinctions, and it is very probable that many 

 of the characters we rely upon to separate the species from one another, 

 will prove to be the effects of différent types of environment. 



It is possible that the character, for example, wliich forms such a strik- 

 ing feature of some of the species of the genus , namely, that the cyclo- 

 systems ail open on one surface of the flabellum , is in some way connected 

 with the flow of the currents of water in which the spécimens are found. 

 iS. tiliatus is one of the species showing this character and S. complanatus 

 of Pourtalès is another. It is of spécial interest therefore to note the curious 

 coïncidence that the Siboga spécimens and the Talisman spécimens of 

 S. tiliatus were obtained from water of exactly the same depth 275 mètres 



33. 



