19 



STATION 273. Anchorage off Pulu Jedan, East coast of Aru Islands, (Pearl Banks). 13 meters. Sand 

 and shells. Plexaura flava, P. recta, Plexauroides prcelonga, P. lenzii. 



STATION 285. 839'.iS., I274'.4E. Timor Sea. 34 meters. On the limit between mud and coral. 

 Lithothamnion. Plexaura attenuata, Euplexaura rubra. 



STATION 299. io52'.4S., i23i'.iE. Cyrus Bay, Rotti Island. 34 meters. Mud, coral and Litho- 

 thamnion. Plexaura recta, Euplexaura mollis. 



STATION 315. Anchorage East of Sailus Besar, Paternoster Islands. Up to 36 meters. Coral and 

 Lithothamnion. Plexaura aggregata, Hicksonella princeps. 



Specimens of Plexaura recta from Pulu Missa near Flores. J. H. DE SlSO don. 

 Plexaura pinnata. Locality unknown, as the label is missing. 



The list shows that Plexauridae were collected at 19 of the stations occupied by the 

 Siboga Expedition. As there appear to be somewhat more than 200 successful hauls from the 

 bottom it follows that members of this family were secured by about io/ of these hauls, 

 showing that the family is meagerly represented in this region in comparison with the Muriceidae. 

 No station yielded more than four species, while one Station (310) yielded no less than 17 

 species of the Muriceidee. 



But two species of Plexauridae were secured at depths of over 500 meters. One of these 

 was Enplexaura reticulata, from a depth of 521 meters-, another was P sammogorgia arbuscula, 

 from a depth of 560 meters. 



The family thus appears to be largely restricted to moderately shallow water, which may 

 in part account for the wide difference between the Atlantic and Pacific plexaurid faunae. 



The genus Plexauroides is the only one in which species previously recorded are found. 

 Plexauroides prcelonga has been reported from Australian waters and Ceylon, and P. lenzii is 

 known to occur near Singapore. Neither of these localities is far from the East Indian region. 



So far as the Siboga material bears testimony concerning the distribution of the Plexauridae, 

 that testimony is negative regarding the occurrence of species in both the Atlantic and Pacific. 

 It is also a notable fact that the genera Eunicea and Plexarirella, both furnishing numerous 

 species from the West Indies, are not at all represented in the Siboga collections. 



As indicated above, the restricted bathymetric range of most of the known species of 

 this family may account for the correspondingly restricted geographic range. Caution must be 

 exercised, however, in drawing general conclusions from the limited information at our disposal. 



