ASPIDOSIPHON CYLINDRICUS. 197 



The layer of longitudinal muscles is continuous, of glister- 

 ing appearance, much thicker in the anterior third part 

 of the body, where at the dorsal side some irregular slits 

 are visible. Two strong retractor-muscles (fig. 2) are attach- 

 ed with broad base near the caudal end of the body, 

 on about ^/- of its length, the left a trifle more anteriorly 

 than the right one; they are fused nearly in the middle 

 of the body. The spiral of the alimentary canal shows 

 nine double coils and is furnished with a complete spindle- 

 muscle, which is attached in the middle of the posterior 

 shield. An other muscle (Befestiger) arises from the place 

 of passage of the oesophagus into the intestinal spiral , 

 passes through the angle between the two retractor 

 muscles and is attached to the body-wall at the left of 

 the nerve-cord. A diverticulum could not be observed. The 

 nephridia are long and slender; they do not extend quite 

 till the end of the retractor-muscles, and the right appears 

 not to be so long as the left one. Over a great part of 

 their length the nephridia are fixed to the body-wall by a 

 mesenteric ligament. 



Of the ten species of Aspido siphon , observed in the 

 Indian Ocean , our specimen most resembles in its external 

 appearance A. Steenstrupii Dies. ^); however, this species 

 belongs to the group having the longitudinal muscles 

 split up into bundles. In structure it more agrees with 

 A. ravus, found by Sluiter in the bay of Bantam and 

 kindly placed by him at my disposal for comparison '^). 

 This species , however, differs from the Kisser-specimen 

 in several external and internal characters. Its body is 

 only 5^/2 times as long as broad , the anal shield is finely 



1) Selenka, de Man und Biillow, Die Sipuncnliden, Taf. I, fig. 12 und 13. 



2) For some of my colleagues I think it interesting to know, that the 

 Museum of the //Koninklijke ^fatuurkundige Vereeniging in Ned. -Indie" at 

 Batavia does no longer exist, and that the Invertebrates, collected and described 

 by Dr. Sluiter, all are transported to the Zoological Museum of ihe Univer- 

 sity of Amsterdam. 



Notes from the l^eyden IVliiseiira, Vol. XX. 



