POLYCHAETOUS ANNELIDS 



37 



Collected at stations and depths as follows: 



(See map 3, p. 58). 



Genus CORYNOCEPHALUS Levinsen 



Corynocephalus paumotanus Chamberlin 



Corynocephalus paumotanus Chamberlin, 1919, pp. 141- 

 143, pi. 23, figs. 1-3 



Collected as indicated below. 



(See map 3, p. 58). 



Corynocephalus magnachaetus n. sp. 



(Plate II, figures 21, 22) 



A slender, elongated species about 20 mm in length 

 and containing about 90 somites. The body is not more 



than 0.5 mm in diameter and the prostomium 0.75 mm. 

 The body width is fairly uniform until near the posterior 

 end where there is a narrowing; the pygidium width be- 

 ing not more than one-fourth that of the widest part of 

 the body. These measurements were made on the type 

 specimen which may not have been fully grown but 

 others agreed fairly well with this. The body is much 

 more slender and there is less overlapping of somites 

 than is the case in C. paumotanus of Chamberlin. 



The prostomium is depressed between the eyes and 

 has a very short median tentacle near its anterior bor- 

 der (pi II, fig. 21). In most individuals, including the 

 type, the prostomium was bent so that no good view of it 

 could be obtained. In the one drawn the left anterior ten- 

 tacle remains, the right one having been lost. The ante- 

 rior tentacles are essentially similar in form and size 

 to the posterior and are bent back under the prostomium. 

 There are five pairs of tentacular cirri, one on the first 

 somite and two on each of the following. The first are 

 small and ventrally placed, each about equal, to tentacle 

 in size. The second and third ventral cirri are succes- 

 sively smaller than the first. The dorsal cirrus of the 

 second somite is considerably larger than the ventral a 

 and the third is still larger. In the one drawn, the head 

 region had been bent so that on the left side the large 

 tentacular cirrus appears to be in contact with the pro- 

 stomium. In his key to the described species of Cory- 

 nocephalus, Chamberlin (1919, p. 141) uses the axes of 

 the eyes in their relation to one another as important 

 features of the diagnosis. Owing to distortion during 

 preservation, or for other reasons, none of the Carnegie 

 material was sufficiently uniform in this respect to be of 

 value in species determination. 



The parapodia carry broad dorsal and ventral cirri, 

 the dorsal being the larger, and anterior ones are small- 

 er than those from near the middle of the body. The se- 

 tae are characteristic in that as far back as somites 14 

 or 15 each parapodium has a bundle of four or five very 

 long heavy ones, radiating fan like from the parapodial 

 surface, there being only a few slender ones. Behind the 

 region of somite 15 the parapodia are larger and carry 

 tufts of long, slender, simple setae; the stout setae as a 

 rule disappear completely. In some specimens the only 

 pigmentation is a small spot on either side at the base of 

 the parapodium, but what seems to be a more typical 

 condition is shown in plate II, figure 22. On the dorsal 

 surface of the otherwise colorless somite fine brown 

 lines outline a trapezoid, the anterior one of these lines 

 being the shorter. Toward their middle these lines show 

 a tendency to break up and be connected by a network of 

 finer lines. From each basal angle of the trapezoid a 

 line extends to the pigment spot on the parapodial surface 

 and a much finer one extends in a loop forward from the 

 anterior angles. 



The type was collected at station 97 in 50 m and is 

 no. 20087 in the United States National Museum. Others 

 were taken in 50 m at stations 2, 44, and 71; and in 100 

 m at stations 74 and 99. See map 3 (p. 58). 



Genus PLOTOHELMIS Chamberlin 



Plotohelmls alata Chamberlin 



Plotohelmis alata Chamberlin, 1919, pp. 144-146, pi. 23, 

 figs. 4-10, pi. 24, figs. 1-3. 



Collected at stations 97 in 50 m and 132 in 100 m. 

 See map 3 (p. 58). 



