RIJKS MUSEUM VAN NATUURLIJKE HISTORIE — LEIDEN 63 



VIII. - ON A NEW GENUS OF APHRODITIDAE FROM THE NETHER- 

 LANDS' EAST-INDIES. 



BY Dr. R. HORST. — (WITH TWO TEXTFIGURES). 



At the Stations 49a and 260 the Siboga-Expedition collected two 

 specimens of Aphroditidae, that, though agreeing in their main characters 

 with Hermione and Laetmonice, in my opinion cannot be ranged in these 

 genera on account of the quite different shape of their dorsal bristles ; 

 therefore the new genus Halogenia may be proposed for them. 



Halogenia arenifera n. sp. 



Siboga-expedition, Stat. 49a, Sapeh-strait, depth of 69 M. 



The body of the unique specimen is ellipsoidal, long 12 mm., broad 

 7 mm. ; the number of its segments is about 30. Its ventral side is rough, 

 densely beset with small tubercles, whereas the dorsum is entirely covered 

 with sand-grains, that are adhering to the elytra. No dorsal felt 

 could be detected. The parapodia are slender, conical, measuring 

 in length two thirds of the breadth of the body. The sides of 

 the body are flanked by long dorsal bristles (fig. 1), that are thin 

 and flexible, pale-brown coloured; they show a fine, longitudinal 

 striation and terminate at their distal end in a large, 

 dark-brown hook, bearing on its convex side a conical point. 

 The bristle is surrounded by a sheath, that (presumably by the 

 influence of the spirit) has a wrinkled appearance and above 

 the hook passes in a rather long filiform appendage, that in its 

 basal part shows a small enlargement. In the anterior segments 

 these bristles are so long, that bent afterwards they almost 

 reach to the end of the body. In front of these uncinate bristles 

 some barbed setae are situated, provided with a rather long 

 spear-tip, behind which two or three recurved fangs occur. Each 

 ventral bristle has about a dozen of spikes and a large spine at 

 some distance beneath them. 



The head is rounded rectangular, somewhat broader than long 

 with a folded ridge at the right and left side. The tentacle has 

 a stout, conical, basal joint, almost half as long as the thead ; its yw. 1. 

 terminal part is broken off. On each side there occurs an eye- 

 peduncle, with a large black spot. The palps are long and tapering; bent 

 backward they reach to the 10'h segment. Also the tentacular cirri are 

 long and slender, provided with a terminal enlargement; the dorsal of 

 them is a third longer than the ventral one. 



