338 THE ANNELIDA POLYCHAETA. 



difference between the two species is in the relationship ventrally between the 

 two achaetous somites. In lucida the second one projects broadly forward to 

 the border of the mouth, thus completely dividing the first one, whereas in 

 telura the second annulus is separated from the first by a deep transverse furrow. 

 It thus diverges not only from species of Oenone, but hkewise from those of 

 Lumbrinereis, etc., in which the first annulus is similarly ventrally separated 

 by the forward protrusion of the second. The lower lip is carried clearly for- 

 ward farther than in lucida. The latter species, according to Augener's inter- 

 pretation, is extremely widespread. He believes it to include the following: — 

 Oenone diphyllidia Schmarda, Oenone pacifica Fischh, and Aglaurides erythraensis 

 Gravier; also possibly Danymene fouensis Kinberg.^ He makes the genus, 

 in fact, monotypic; but I am convinced that the form above must be held to be 

 different unless the variability in maxillae II, of the crochets, and especially in 

 the relation of the first somites, are much greater than is indicated by present 

 evidence. 



DORVILLEIDAE. 



In these annelids the body is composed of but a moderate number of somites 

 and is slender and cylindrical in shape, or sometimes fusiform. 



The prostomium is distinct and is rounded, horseshoe-shaped to quadrangu- 

 lar and pentagonal in outUne. It bears a pair of palpi, one pair of articulated 

 tentacles, or else four similar, nonarticulated appendages. Eyes four. Nuchal 

 organs primitive, open, cihated surfaces. 



The first two somites lack appendages. 



The parapodia are structurally biramous, though in appearance uniramous, 

 having ventral cirrus and dorsal cirrus with a basal joint or cirrophore supported 

 by an aciculmn. 



The dorsal fascia of the parapodia consists of simple setae, the ventral of 

 composite ones. 



The pygidium bears either two or four anal cirri, when four are present 

 two being shorter than the others. 



The proboscis armed with a pair of mandibles and numerous maxillae in 

 two series. 



Swarming at the surface of the ocean similar to that occurring in the Palolo 

 worms, mentioned under the Leodicidae, is known in the family and has been 

 described in detail for Dorvillea gregarica} 



' Cf. Augener, Fauna Sudw.-Austr. Polych. 1, 1913, 4, p. 290. 

 ^CJ. Mayer, Bull. M. C. Z., 1900, 36, p. 1. 



