HOLOTHUEIANS OF NEW ZEALAND. 25 



dunedinensis is stown to be unisexual, as opposed to the herma- 

 phrodite condition supposed to be characteristic of the genus. 



A little-known type of spicule is described in a species of 

 Sficho^us (&gs. 83-87) ; and some apparently new facts concerning 

 the structure and development of the wheels of Chirodota are 

 given in the Appendix. 



The arrangement of the genera is that followed in the ' Chal- 

 lenger ' Eeport. 



3. The New Zealand Species. 



Stnapta uncinata, Hutton. 



1872. Synapta uncinata, Hutton, Cat. Echinoderm. N. Z. p. 16. 



1886. Synapta uncinata, Theel, ' Challenger ' Holothurioidea, p. 27. 



The original description runs : — " Body curved, ? tapering 

 behind, broadest at the mouth ; tentacula thirteen, very short, 

 merely tubercles, with two incurved hooks at the end of each. 



" Pale reddish-brown. 



" Length •& : breadth at anterior end '2. 



" Dermal plates anchor-shaped ; the flukes equal." 



A small jar in the Wellington Museum, labelled " 31. Synapta 

 uncinata^'' contained what is evidently the type and only known 

 specimen of this species. The specimen is merely the anterior 

 end of the animal, about half-an-inch in length, bearing the crown 

 of thirteen tentacles. The individual to which it belonged may 

 have been of considerable size, probably at least four or five 

 inches in length. The thirteen tentacles are of equal size and 

 arranged in single series. In their present contracted state they 

 are short and stumpy, and each bears four incurved digits at its 

 extremity, the two inner ones being larger than the two outer. 

 They are evidently the two larger digits to which Hutton refers 

 under the name of " incurved hooks." Each tentacle also bears 

 along each margin, and facing inwards, a double row of small pro- 

 jections which are indistinguishable from sucker-bearing tube-feet. 



On cutting the specimen open, I found the madreporic ring 

 and its appendages still in a fair state of preservation. There 

 were nine long, straight, slender Polian vesicles and three 

 madreporic canals. Of the latter, two were branched and slightly 

 convoluted ; the other much convoluted, but apparently not 

 branched. The madreporic canals were situate dorsally, on the 

 same side as the mesentery. The longitudinal muscles were very 

 strongly developed, and there were no retractors. 



