REPORT ON TEE ASTEROIDEA. 1G1 



The mouth-plates are large, prominent, and elevated along the line of suture ; the 

 junction is imperfect, and the adoral extremities of the plates being widely open expose 

 the odontophore. Their armature consists of six to eight mouth-spines on each plate, 

 which are short, compressed, and pointed. The innermost one on each side is larger 

 and longer than the rest, and is directed towards the actinostome ; the lateral ones 

 stand in the furrow and interlock with the corresponding denticles of the neigh- 

 bouring mouth-angle. A number (varying from six to twelve) of small granule-like 

 tubercles are present on the actinal surface of each plate ; two, which are slightly largest, 

 stand near the inner third of the plate, whilst the remainder are confined to the aboral 

 half of the plate, and are sometimes arranged in two or three lines, and sometimes 

 irregularly. It seems scarcely possible to rank these as secondary mouth-spines ; and 

 yet there can be little doubt that they are rudimentary or aborted representatives of 

 these appendages. 



The actinal interradial areas are triangular in outline, and covered with a regular 

 plating of hexagonal, imbricating, scale-like intermediate plates arranged in columnar 

 series extending from the margin to the furrow, parallel to the median interradial 

 line. The plates are broader than long, the disproportion increasing as they approach 

 the margin ; they bear a few (three to five) small, widely spaced, irregularly disposed 

 granules, some plates here and there having none. 



Colour in alcohol, greyish white on the margins and actinal area ; abactinal membrane 

 bluish grey, with touches of light brown near the margin of the area and occasionally 

 on the groups of paxillae round the centre of the disk. 



Locality, — Station 299. Off the western coast of South America, between Valparaiso 

 and the Island of Juan Fernandez. December 14, 1875. Lat. 33° 31' 0" S., long. 74° 

 43' 0" W. Depth 2160 fathoms. Blue mud. Bottom temperature 35°*2 Fahr. ; surface 

 temperature 62 o- Fahr. 



Remarks. — Hyphalastcr diadematus is distinguished from the other members of 

 the genus by the prominent groups of larger paxillse on the abactinal area of the disk 

 (the character from which the name is derived), and by the presence of five cribriform 

 organs. 



The example of this species, which is figured on PI. XXL, did not come into my hands 

 until some time after the preliminary notice 1 of this group had been published. It 

 was one of the two species which had been drawn under the direction of the late 

 Sir Wyville Thomson before the collection was entrusted to me, and after his death 

 the specimens had been mislaid amongst other things, and were lost sight of for 

 some time. 



The type which has been described is larger and differs slightly in several respects, 

 but I see no reason to doubt for a moment that the two examples belong to the same 

 1 Journ. Linn. Soc. Lond. (Zool.), 1883, vol. xvii. p. 237. 



(BOOL. CHALL. EXP. PART IX 1887.) - 1 



