40 APwT. 4. — I. TKEDA : 



ASPIDOSIPHON STEENSTRUPII, Diesinc. 



Selenka (28), 1883, p. 116. 



The main characters of this species, taken from Selenka's 

 description, are as follows : 



Introvert and body proper nearly equally long. Color light 

 yellowish brown, nearly black at both ends of body proper. 

 Skin-bodies formed of closel}^ aggregated polygonal plates, four 

 or more of AYhich lie in the center ; each of the latter plates 

 with a small plate. The two shields are of a nearly flat hemi- 

 spherical form, lightly grooved radially and circularly ; formed 

 of small oval or polygonal bodies, those lying in the periphery 

 being largest. Introvert with small double-toothed hooks ar- 

 ranged in complete rings and with a great number of relatively 

 tall perforated papillœ (" Ausmündungspapillen "). Longitudinal 

 muscle, in the posterior part, separating into about 25, frequent- 

 ly anastomosing bundles ; anteriorly these gradually diminish in 

 number till they all coalesce into a continuous layer. Retractor 

 muscles spring from the beginning of the posterior fourth of the 

 body j)roper, the line of their origin extending from the 3rd to 

 the 7th (sometimes to the 8th) longitudinal muscle. Spindle 

 muscle fixed to body-wall at both ends. Rectal diverticulum 

 present. Fixing muscle said to be absent, except in specimens 

 from the Philippines, from which Selenka has described a 

 single fixing muscle attached to the 1st or the 2nd intestinal 

 spiral. No contractile villi. Segmental organs long, posteriorly 

 reaching to the roots of the retractor muscles ; their anterior 



