261 



In the tentacles there are no rods, but only oval bodies. These 

 in the tentacle-base (Fig. 48. 14) vary in size from 10 to 40 /// in 

 diameter. The calcareous deposits in the digits are nearly ring- 

 shaped, the central part being more or less dissolved (Fig. 48. 15). 



Protankyra pseudo-digitata Semper is the most closely related 

 to bidentata Woodward & Barrett and to bankensis Ludwig, but it 

 differs distinctly from both species. In the description of digitata 

 it is said that the best characters for distinguishing it and pseudo- 

 digitata are the shape of the ciliated funnels, the deposits in the 

 tentacles and the large anchor-plates, and the two species cannot 

 be confounded when these organs are present. According to Lud- 

 wig (Beiträge zur Kenntniss der Holothurien pag. 78) bankensis 

 differs from pseudo-digitata in having dented holes in the anchor- 

 plates and in having serrate arms on the small anchors. These 

 characters do not separate the two species distinctly, as some of 

 the small anchors in pseudo-digitata may have serrate ams and 

 the holes in the plates are usually toothed; but that the two species 

 are distinctly different, appears from the shape of the anchor-plates 

 in bankensis. Furthermore Ludwig states that cross-shaped and 

 stellate bodies are wanting in the skin of bankensis. If this is 

 really the fact, it will be a valuable character for separating the 

 two species. Although I consider bankensis as a valid species, 

 I have no doubt that innominata Ludwig is synonymous with pseudo- 

 digitata. In the description of innominata Ludwig writes: "Die 

 grossen Anker kommen nur in den fünf Radien des Körpers vor." 

 This does not agree with the specimens at hand, and as it is also 

 contrary to Ohshima's remarks of bidentata in "Die Synaptiden 

 von Misaki", I suppose that it may be a mistake. 



That molesta Semper may rather be referred to pseudo-digitata 

 than to bidentata is probable from the shape of the anchor-plates, 

 which quite agree with the small plates in pseudo-digitata. Further- 

 more the size of the ciliated funnels in molesta agree much better 

 with that of the funnels in pseudo-digitata, than with that of the 

 funnels in bidentata. 



In the report on the Echinoderms from the Suez Canal, collected 

 in 1924 by the Cambridge Expedition, Dr. Mortensen describes 

 some few specimens of a Protankyra; he has not identified the spec- 

 imens, but supposes that they are identical with or at any rate closely 



