36 



it is shown in fio\ 179, where we observe that the cloaca extends far more distally. In Dondersia 

 festiva dors. .-terminal sense-knots also occur, 2 of which I can positively demonstrate. I hope 

 to make close observations of Dondersia festiva afterwards, but I take it for„ certain that both 

 forms are closely related. 



Dondersia differs from Stylomenia in the structure of the nervous system and radula, 

 and in the absence of the "organes en cordon", met with in Stylomenia. Yet there is, no doubt, 

 a close relation with Stylomenia (cf. spicula, vestibulum, salivary glands, radula, cloaca-ducts of 

 Stylomenia). 



New diagnosis for Dondersia. 



Dondersia Hubrecht. 



Body long, length-index 10 — 48. 1 ventral fold. Spicula needie- or spatula-shaped, flat. 

 Cuticle very thin, no papillae. Dorso-terminal sense-knots present. 1 pair of short ventral salivary 

 glands, which unite before opening out into the pharynx. Radula small, monoserial (4? teeth). 

 Mouth-cavity and pharynx-opening separated from each other. No copulation-spicula. 



festiva Hubrecht. 



Length-index 10. Violet; the proximal part of the body thickened. 2 Dorso-terminal 

 sense-knots. 1 pair of tubular and 1 pair of vesicular appendages of the cloaca-ducts. 

 Naples. 



annulaia nov. spec. 



Length-index 48. Pale brown with 30 white non-closed rings. 3 dorso-terminal sense- 

 knots. 1 pair of vesicular appendages of the cloaca-ducts. 

 East-Indian Archipelago. 1 Specimen. 



Chaetoderma. 



12. Chaetoderma Lovéni nov. spec. (Plate VI, figs. 180 — 203). 



Stat. 35. 8°o'.3 S., n6°59'E. 1310 M. In mud. 2 Specimens and a fragment. 



Length 15 — 21 mm.; length-index of the two known specimens 20 and 34. Colour 

 vellow-brown. Proximal part considerably thickened, distal part narrow but ending in a little 

 knob. Extremely glittering owing to the flat and broad spicula. Radula with 1 large tooth, 

 2 sickle-shaped teeth, 1 slender oblong tooth and different smaller ones (?). 4 salivary glands. 

 Liver very large, extending as far as the proximal part of the body. 3 Pairs of gill-retractors 

 and 1 large protractor. From 8 to 1 2 gill-lamellae. Ganglion posterius superius situated in 

 the pericardium. 



East-Indian Archipelago. 3 Specimens. 



Figs. 1 80 and 1 8 1 represent the two specimens. The length of the first specimen is 

 16 mm.: the diameter of the proximal part is 1.2 mm. and of the distal part 0.4 mm.; the 

 length-index is therefore 20. 



