﻿432 PROCEEDINGS OF THE NATIONAL MUSEUM vol. lOi 



specimen of nigrescens has reddish brown nephridia with conspicuously- 

 inflated proximal portion, but the distal part is badly contracted. 

 The contractile vessel has no villi, and there is no sign of them in the 

 Hawaiian specimen of nigrescens, although Selenka states that they 

 are present in that species. 



Type locality. — Puntarenas, Costa Rica. 



Distribution. — Panama to Gulf of California. 



Specimens examined. — Five, as follows: 



Esplritu Santo Islands, near La Paz, Baja California, March 1940, E. F. Ricketts, 



1 specimen. 

 Guaymas, Mexico, Miramar Beach, rocky, Feb. 10, 1948, W. H. MacGinitle, 



1 specimen. 

 Bay of Panama, F. H. Bradley, 1866, 3 specimens. 



Remarks. — This species seems to me to be of tropical derivation and 

 closely related to Ph. nigrescens Keferstein, 1865, whereas agassizii is 

 primarily a cold-water species, which reaches its best development 

 both in size and number of individuals from Alaska to northern 

 California. South of Monterey Bay large specimens are apparently 

 absent or else are to be found in cooler water off shore. 



PHASCOLOSOMA DENTIGEEUM (Selenka and de Man) 



Plate 39, Figures 4-7 



Phymosoma, dentigerum Selenka and de Man, 1883, p. 67, pi. 1, fig. 9; pi. 9, 

 figs. 118-123. 



Diagnosis. — Medium-sized, slender species with a dorsal preanal 

 area of conspicuously enlarged, dark-brown, sharp conical tubercles, 

 some of which are usually directed backward ; a similar area of sharp 

 conical tubercles at posterior extremity; other papillae small; rings 

 of hooks few; hooks sharply bent, with a median, often slightly 

 dilated, clear streak and a separate large triangular clear area. 



Description. — The specimens are all slender; one with introvert 

 fully extended measures: trunk 30 mm., introvert 20 mm. A larger 

 example, with introvert retracted, would attain a length of 67 mm. 

 General color of preserved specimens yellowish gray, pale sepia, 

 or pinkish lavender. Longitudinal muscle bands visible through 

 body wall. Papillae of ventral surface very small, gradually increasing 

 in size to middorsal region, where in anterior half of trunk they are 

 still small and of unequal size. Posteriorly, however, they rapidly 

 increase in size to become circular, conical, sharp, dark brown tubercles 

 against the pale ground color. Immediately in front of the anus 

 is a ring zone of the same sharp brown tubercles. These are continued 

 forward on the introvert as a middorsal band for about half to two- 

 thirds its length, usually, but not always, in conjunction with a skin 

 color of burnt-sienna, which makes the area very conspicuous. The 

 largest tubercles are at the base of the introvert and are directed 



