148 COLLECTIONS FROM MELANESIA. 



almost black), the differences in the extent to which the papilla? are 

 developed, and the comparatively much greater firmness of the 

 integument of the younger specimens help us to understand how it 

 is that several different names have been given to this widely dis- 

 tributed species. On the other hand, it is well to still bear in mind 

 that our knowledge of Holothurian organization is not yet so com- 

 plete as to justify us in definitely asserting that fresh differential 

 marks do not yet remain to be discovered ; if there are such, the 

 series now regarded as single may be shown to contain represen- 

 fcatives of more than one form. 



As the only illustration of the spicules appears to be that which 

 has been given by Prof. Semper, I have had views made of them 

 from the side to show the characters of the free projecting processes, 

 and from below showing the inside of the hemisphere. 



Port Mollc : Port Denison ; Torres Straits ; Alert Island (Torres 

 Straits), 17 fms., sand. 



6. Colochirus australis. 

 Ludwig, Sempef's Arbeiten, ii. p. 88. 



This species, which is represented by only one specimen from Port 

 Molle (14 fms.), was more richly so in a collection forwarded some 

 three years ago from Port Jackson by Mr. J. Brazier. I do not, 

 however, find that the suckers are in them brown in colour, while 

 the tentacles are rather black and white than brown and yellow. 

 Neither of these are, however, points of any real importance. I 

 find, from Mr. Eamsay's collections, that this species is very abundant 

 in Port Jackson. 



7. Actinocucumis difficilis. (Plate IX. fig. C.) 



I have had the greatest difficulty in assuring myself of the specific 

 distinctness of this form from the A. typica of Ludwig, the varia- 

 tions exhibited in the present collection impressing one with the 

 necessity of the greatest care in the delimitation of species. 



The species may perhaps be most conveniently described by 

 pointing out the several characters by which it is to be distinguished 

 from A. typica. The ambulacral papillas on the dorsal surface are 

 rare, and the suckers are not in more than four rows for each ray ; 

 the differences in the form of the spicules will be best seen by com- 

 paring the figures now given with those drawn by Professor Ludwig. 

 The retractors are inserted rather further back, being found at 24 

 millim. from the anterior end in a specimen 65 millim. long, and 

 at 22 millim. in one 70 millim. long ; the genital tubes are shorter 

 than in A. typicd, being not more than 15 millim. long in any speci- 

 men examined. The Polian vesicle would also appear to be shorter, 

 being only 7'5 millim. long in a specimen of 65 millim. length. It 

 may be added that the loop of the intestine is exceedingly short ; 

 that the tentacles, which are not always 20, sometimes seem to 



