i9oS. Southern. — A New Irish Gephyrean. 173 



ciliated on their inner surfaces. In living specimens the 

 movements of these cilia can be easily seen under the micro- 

 scope. 



The genus Petalostoma, of which this is the only species 

 described, is characterised by the leaf-like tentacles, absence 

 of a vascular sj'stem, fused retractor-muscles, and the structure 

 of the nephridia. The bulb at the end of the oesophagus is 

 an unusual structure in the Sipunculoidea, to which this 

 genus belongs ; but in the Kchiuroidea, a muscular organ, the 

 crop, is usually present in a similar position. 



Description of Pi.ate 9. 



Pctalosfonia i/iiiiitiu/ii. 

 Fig. I.— General anatomy, a. bulb at the end of the oesophagus. 



b. retractor muscle. 



c. ovary. 



d. nerve-cord. 



e. nephridium. 



/. ovum, in the body-cavity. 



g. anus, 



h. tentacles. 

 Fig. 2. — Animal, x \\. 

 Fig. 3. — Nephridium. a. external opening. 



b. ciliated funnel, opening into the body- 

 cavity. 

 F"ig. 4.— Ovary. a. ova. 



b. stomach. 



c. retractor muscle. 



d. nerve-cord. 



Fig. 5.— External appearance of the epidermis, highly magnified, 

 showing dotted pigment and papillae. 



National Museum, Dublin. 



A3 



