42 PEOF. A. DENDY ON THE 



coDstriction from the globular, thick-walled stomach, which is 

 followed by a long and rather wide thin-walled intestine. 

 Eectum very short, attached to the body-wall by radiating 

 muscle-fibres. The two respiratory trees are well developed and 

 copiously branched as usual. 



There are four long, narrow Polian vesicles, and a single 

 dorsal madreporic canal running in the mesentery close to the 

 genital duct as usual. The Polian vesicles and madreporic canal 

 are arranged at approximately equal intervals round the ambu- 

 lacral ring. The ampullae of the tube-feet are few and small. 



The reproductive organs consist of two bunches of short cseca 

 attached one on each side to the dorsal mesentery far forward, 

 alongside the cesophagus. 



The spicules are small, oval, reticulate plates (PI. 7. figs. 70-72), 

 very sparingly scattered through the integument. Diameter 

 about 0"1 mm. Some of them have small warts on the surface. 



The type specimen from which this description was taken was 

 collected at Macquarie Island, and given to me by Professor 

 Parker, and I have since received through Mr. H. Suter four 

 smaller specimens collected at the same place by Mr. A. Hamilton, 

 and evidently belonging to the same species. Two of these still 

 show in spirit a distinct purple tint on the dorsal surface, which 

 appears to be normally quite smooth. 



Thyonidium longidentis, Hutton, sp. (PI. 6. figs. 62-69.) 



1872. Thyone longidentis, Hutton, Cat. Echinoderm. N. Z. p. 16. 



1872. Thyone caudata, Hutton, Cat. Echinoderm. N. Z. p. 16. 



1879. Pentadactyla longidentis, Hutton, Trans. N. Z. Inst. vol. xi. 

 p. 307. 



1886. Thyonidium rugosum, Theel, ' Challenger ' Holothurioidea, p. 95, 

 pi. V. fig. 6. 



1886. Thyone longidentis, Theel, ' Challenger'' Holothurioidea, p. 141. 



1886. Thyonidium caudatum, Theel, ' Challenger ' Holothurioidea, p. 147. 



1891. Phyllophorus caudatus, Ludwig, Bronn's Klassen und Ordnungen, 

 Echinodermen, p. .347. 



1891. Phyllophorus rugosus, Ludwig, Bronn's Klassen und Ordnungen, 

 Echinodermen, p. 347. 



It is only after much trouble that I have arrived at the conclu- 

 sions expressed in the above synonymy, from which it will be seen 

 that I regard three "species" hitherto kept separate as identical. 

 My chief reasons for this conclusion are — the identity in structure 

 of the extremely complex calcareous ring in all three, the identity 



