1890.] NATURAL SCIKNCES OF PIIII.ABELPIIIA. 821 



In the specimen obtained there are twenty tentacle.s of nearly 

 uniform size. 



The body wall i.s thick. 



The calcareous rinij is well d('velo])ed, but its conipoueut j^ieces 

 are not very coherent. 



There are numerous short madreporic canals, arranged in two 

 l)undles, one on either side of the dorsal mesentery above the 

 •esophagus, three on the left side and ten on the right. The distal 

 portion of each canal is enlarged, forming an elongated head as in 

 the preceding species. 



There is one long and slender Polian vesicle, more than half the 

 length of the animal, with two considerable vesicular enlargements, 

 one near its end, and the other near its middle. 



The specimen possesses a very small bundle of Cuverian organs. 



The color in alcohol is a dirty white mottled with dark gray. 

 The dark gray predominates on the anterior portion of the dorsal 

 region. The tentacles are a dirty white, the walls of the })edicels 

 and papilke light gray, and the disks of the })edicles straw-colored. 



Ivength of the specimen, 80 mm. 



Collected at the Port of Silam among the wet sea-weed of the 

 beach. 



This form is characterized by rosette-like plates, absence of tables, 

 two bundles of madreporic canals, non-stellate anus, absence of wart- 

 like prominences on the dorsal surface, general distribution of pedi- 

 cels and the very small number of papillae. The number of tenta- 

 cles, presence of Cuverian organs and character of its Polian vesi- 

 cle, are probably not important characters, on account of the want 

 of stability of structure of these organs. 



It falls into the section of the genus Holothuria defined by Theel 

 as " possessing more or less incomplete rosettes." Seven species are 

 included by him in this section, H. marmorata J'dger, H. Argus 

 Jiiger, H. Vitiensis Semper, H. tenuissima Semper, H. KoeUikeri 

 Semper, H. clemens Ludwig and H. similis Semper. He thinks it 

 probable, however, that they represent one or more species capable 

 of great variation.. They have hitherto only been reported from the 

 tropical Indo-Pacific region. 



Holothuria Silamensis differs from all of them in the possession of 

 two well-developed bundles of madreporic canals, instead of a single 

 canal. It can also be distinguished from H. marmorata, H. Argus 

 and H. Vitiensis, by the circular instead of stellate anus ; from H. 



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