POLYCHAETOUS AMNELIDS 



41 



FAMILY NEREIDAE 



Genus NERE3S Linnaeus 



Nereis slngulaxis n. sp. 



(Plate III, figures 33-37) 



The type is 8 mm long and 0.5 mm wide at the pro- 

 stomium, tapering toward the posterior end. The pro- 

 stomial length is about equal to its width, its greatest di- 

 ameter being just in front of the anterior eyes (pi. Ill, 

 fig. 33). The tentacles are separate to their bases, rath- 

 er stout, and nearly as long as the prostomium. The 

 palps have globular basal joints and narrower terminal 

 ones which are more or less distorted in the specimen 

 from which the drawing was made. The eyes are rep- 

 resented by two irregularly shaped masses of brownish 

 pigment spots in which no indication of the usual sepa- 

 ration into two pairs of eyes can be seen. The first so- 

 mite extends rather far forward by the sides of the pro- 



stomium. The longest tentacular cirrus is the dorsal one 

 of the second pair which extends to somite 9. 



In the parapodium the dorsoventral diameter is some- 

 what less than that of the somite, its setal lobes being 

 about equal in length. The dorsal cirrus is very long 

 (pi. Ill, fig. 34), and the lobe which carries it is longer 

 than the others. The ventral cirrus is very short. There 

 are three kinds of setae. The most ventral ones are 

 compound and have short terminal joints (pi. Ill, fig. 35) 

 which are bent at the ends. Dorsal to these, and making 

 up most of the dorsal bundle, are other compound setae 

 whose terminal joints are long and slender, and toothed 

 along one margin (pi. Ill, fig. 36). In the dorsal bundle is 

 a single much larger compound seta having the form 

 shown in figure 37. 



The type is no. 20092 in the United States National 

 Museum and was collected at stations 13 and 14 at the 

 surface. See map 4 (p. 59). 



LARVAE AND GENERIC ALLY INDETERMNABLE MATERIAL 



HETERONEREIDS 



Heteronereids were numerous in a sample takfn at 

 Easter Island and another at Guam, but no attempt v,'as 

 made at identification. 



SPIONIDS 



The collections also contain pelagic larvae of uncer- 

 tain relationships which show certain resemblances to 

 larvae described by Hacker (1898). Hacker identified 

 some larvae as soionids, and though none bore any very 

 close resemblance to those of the Carnegie collection, it 

 is quite possible that some of the latter belong in this 

 family. Hacker gave the type name "Rostraria" to lar- 

 vae characterized by a peculiarly shaped prostomium 

 bearing large eyes, posterolateral prolongations, and a 

 pair of very heavy tentacles which may be longer than 

 the entire body. On either side of the first somite is a 

 tuft of long setae. Hacker described four groups of these 

 larvae so definitely distinct from one another that he 

 gave them specific names. One specimen of the Carne- 

 gie collection is very close to Hacker's R. galatea (1898, 

 pi. IV, fig. 33) but is not sufficiently well preserved for 

 the author to attempt a species diagnosis. HScker 

 thought that his larvae probably belonged in the family 

 Disomidae. 



LARVA A 



The body is 5 mm long and 0.5 mm wide in the wid- 

 est part. The prostomium (pi. Ill, fig. 38) has a width 

 nearly twice its length, and on its dorsal surface are two 

 pairs of eyes of which the larger are nearer the lateral 

 margin. The peristomium is nearly four times as wide 

 as the prostomium and three times as long. On either 

 side it carries a cirrus and a tuft of about ten very 

 heavy setae which carry numerous spines on their sur- 

 faces (pi. in, fig. 39). The next somite is much shorter 

 than the first and has on either side a small ovoid dor- 

 sal, and much larger ventral cirrus. Between the two is 

 a small tuft of slender curved setae. In the next somite 

 the dorsal cirrus is essentially the same as before ex- 

 cept that it is larger and the setae ventral to this dorsal 



cirrus are larger. In this somite two setae appear ven- 

 tral to the larger (ventral) cirrus, one being slender, 

 the other much larger and spiked along the margin. In 

 later somites the arrangement is that two large spiked 

 setae lie just ventral to the elongated oval dorsal cirrus, 

 between it and the ventral cirrus. Ventral to the ventral 

 cirrus is a seta tuft containing only two setae; one very 

 slender, the other spiked. The latter are much smaller 

 than those in the dorsal bundle. Posteriorly the somites 

 become much shorter and narrower; the long dorsal cir- 

 rus and heavy setae disappear. The pygidium (pi. Ill, 

 fig. 40) is broad and carries a large tuft of cilia on eith- 

 er side. In the specimen figured the twenty -second, 

 twenty-third, and twenty-fourth somites were ciliated 

 dorsal to the parapodium. The author could not deter- 

 mine if this extended across the dorsum. 



Collected at stations 39 and 40 in 50 m. See map 4 

 (p. 59). 



LARVA B 



Possibly a later stage of A, though it may belong to 

 a different species. The pygidium is not ciliated but ap- 

 proaches the definite form of a spionid. The prostomi- 

 um (pi. Ill, fig. 41) is broadly rounded and carries two 

 pairs of eyes of which the lateral are nearer the ventral 

 surface than are the median, and in the mounted materi- 

 al they show only faintly through the overlying tissue. 

 There is a short anterior median tentacle and a heavy 

 tentacle on either side. The peristomium is similar to 

 that of larva A, with its cirri and tuft of heavy spiked 

 setae (not shown in fig. 41). 



The specimens were poorly preserved but so far as 

 the author could tell, the arrangement of cirri and setae 

 in the anterior body region is exactly as described for 

 larva A. Posterior to the region of somite 20 the body 

 form changes as in larva A, but gills are beginning to 

 appear on the dorsal surface of each somite in these 

 posterior somites. Two somites composing the pygidi- 

 um have no parapodia or setae but are much flattened 

 and their margins are covered with pigment spots. 



Collected at stations 53 and 54 on the surface. See 

 map 4 (p. 59). 



