293 me. t. p. bedford ox mat.ayax echixoderms. [mar. 20, 



15. Eetaster cbibkosus. 



Pteraster cribrosus, von Martens, Arch. f. Naturg. 1867, p. 109, 

 Taf. iii. fig. 2. 



Retaster insignia, W. P. Sladen, ' Challenger' Eeports, vol. xxx. 

 Asteroidea, 1839, p. 482. 



References. M. Sars, Ofv. af JVorg. Ech. Christiania, 1861, 

 lab. 4. J. O. E. Perrier, Eevision des Stellerides, 1875, 

 p. 383. L. Doederlein, Semon's Zool. Forsch. in Austr. &c. 

 Ed. v. Lf. 3, 1896, p. 319. 



Locality. Four specimens, two of which are quite young, in 

 10-15 fathoms, Singapore. 



Distribution. Zanzibar, Mozambique, Ceylon, Philippines, Am- 

 boina, Samoa (Doederlein). 



The largest specimen agrees with Dr. Doederlein's description 

 of a specimen from Ainboina. The colour, when alive, of all 

 four specimens was bright brick-red, but they rapidly become 

 colourless in spirit ; when alive, the osculum can be seen to open 

 and close with a fairly regular rhythm of about once every ten 

 seconds. Sars has given an account in Pteraster militaris of the 

 osculum bounded by five lappets and of the cavity into which it 

 leads, situated between the dorsal membrane and the true abactinal 

 surface of the body, and in direct communication with the exterior 

 by a large number of short straight tubes in the former and lined 

 by a columnar epithelium ; it appears to function in both sexea 

 as a respiratory chamber, and secondarily in the females as a brood- 

 pouch ; but my want of knowledge of Norwegian has prevented 

 me from understanding Sars's paper as much as I should have 

 wished, but the relations appear to be the same in this species. 

 The reticular arrangement of muscle-fibres in the dorsal membrane 

 is only apparent under a microscopical examination. 



In addition to these 15 species there were two species of Asteri- 

 nidce, each represented by a single specimen. 1 cannot identify 

 them as belonging to any known species ; but as they both appear 

 to be young forms, it seems advisable to defer description until a 

 later date, when a fuller series may be obtainable : they belong 

 to the genera Patiria and Asterina respectively. 



EXPLANATION OF THE PLATES. 

 Plate XXI. 



Pig. 1. Bhabdocidaris atimdijcra, p. 274. 



a. Spines from an iuterambulacrum of specimen No. 1. Nat. size. 



b. ,, ,, „ No. 2. Nat. size. 



c. ,, ,, „ No. 4. Nat. size. 



d. „ ,, „ No. 6. Nat. size. 

 (Vide table of measurements in text, p. 27(5.) 



The spines are so arranged that the uppermost in each series is that 

 which lies nearest to the calycinal system of the test, the lowermost being 

 that which borders on the actinostome ; they are also laid flat, so that 

 their basts lie next to the adjacent ambulacrum, their points being directed 

 towards the centre of the interambulacrum ; no attempt has been made 



