﻿424 PROCEEDINGS OF THE NATIONAL MUSEUM voi. m 



a?. No hooks; tentacles long, filiform, very numerous (50 to 200) ; introvert half 

 length of trunk or less, robust; trunk dark brown from very numerous 

 papillae antillarum Grube and Oersted (p. 434) 



PHASCOLOSOMA AGASSIZn Keferatein 



Plate 36, Figures 3-6; Plate 37, Figures 4-15; Plate 38; Plate 39, Figure 1 



Phascolosoma Agassizii Keferstein, 1866, p. 218; 1867, p. 46, pi. 6, figs, 3, 4, 7. 



Phascolosoma lordi Baird, 1868, p. 92 (Vancouver Island, B. C.) 



Phymosoma Agassizii Selenka, 1883, p. 78. 



Physcosoma agassizii Chamberlin, 1919, p. 30; 1920, p. 5d. 



Physcosoma japonicum Chamberlin, 1920, p. 5d. 



Description. — Size of preserved specimens, with introvert extended, 

 upward of 140 mm. but commonly half that; trunk cylindrical; 

 posterior extremity bluntly pointed. When fully extended the dis- 

 tance from anus to tentacles is three-fourths that from anus to posterior 

 extremity. The body wall varies from slightly translucent to opaque 

 and the skin color from pinkish gray or yellowish gray or pale sepia 

 to reddish brown and dark neutral brown. The lighter colored 

 animals often have a few spots on body (dark purplish brown, neutral 

 brown, reddish brown), which are either obscured or are not present 

 on the darker forms, while the introvert, which is light in shade even 

 when the trunk is dark, is marked by irregular transverse bands and 

 patches of the same variations as the spots, usually along its entire 

 length but sometimes only on the distal part. The skin is rough to 

 the touch from very numerous convex or conical skin papillae of a 

 darker brown than the skin but with a light center. They are smallest 

 midventrally, increasing in size dorsally; and are largest dorsally at 

 posterior extremity and over an area just in front of the anus. Here 

 the papillae are very dark brown, horny, acorn shaped or conical, 

 or in some cases compressed and expanded at base (pi. 38, fig. 31). 

 In front of the preanal area the papillae rapidly decrease in size on 

 the introvert. The relative size of the platelets of the skin-gland 

 papillae is rather constant in specimens of different sizes and from 

 different parts of the geographic range. An example from posterior 

 to anus of a medium-sized example is shown somewhat flattened 

 (pi. 36, fig. 3). 



There are 15 to 25 rings of hooks starting a short distance behind 

 the collar, those of the first three to five rows being very small and 

 colorless. Usually there are about 17 rings clearly visible; the last 

 one or two may be incomplete. Twenty-five figures of hooks on 

 plates 20 and 21 give a fair idea of the variation in the proportion of 

 height to base, size of basal piece, the form and position of clear 

 streak, and the triangular spot. All are drawn to the same scale. The 

 expansion in the clear streak may disappear entirely, even in specimens 

 which have it in some of the hooks (pis. 36, 37) . The so-called tooth 



