REPORT ON THE ASTEROIDEA.’ 465 
Adambulacral plates with an armature forming with that of the infero-marginal plates 
(and actinal intermediate plates if present) a transverse series of large, single, isolated 
spinelets, invested with membranous sacs. (Six are present in transverse series in the type 
form.) 
Mouth-plates with a prominent median keel. Armature consisting of : (1.) A marginal 
series of six mouth-spines on each plate, the innermost one much larger than the others ; 
all invested with membrane. (2.) On the actinal surface of the plate is one large 
secondary mouth-spine in a membranous sheath, placed immediately behind the large 
innermost marginal mouth-spine. . 
Madreporiform body very large and irregularly oval in outline, the margin being 
festooned. Surface grooved with numerous fine striations. 
Ambulacral furrows wide. Tube-feet large and crowded, forming four rows ; with a 
fleshy, button-like, terminal disk. 
No pedicellariz of any kind present. 
Remarks.—This handsome and well-characterised form is undoubtedly allied in many 
points of structure to Korethraster. Peribolaster is, however, at once distinguished by 
the reticulate abactinal skeleton, by the cruciform plates composing it, by the sheathed 
fascicules of the abactinal plates, by the presence of papule on the abactinal surface, by 
the extraordinarily large madreporiform body, and by the quadruple series of ambulacral 
tube-feet. 
Chorology of the Genus Peribolaster. 
a. Geographical distribution :— 
Pactric : One species between the parallels of 45° and 50° S. 
Peribolaster folliculatus, off the west coast of Patagonia. 
8. Bathymetrical range: 45 fathoms. 
y. Nature of the Sea-bottom: Green sand. 
Chorological Synopsis of the Species. 
| 
Ocean. Range in Fathoms. Nature of the Sea-bottom. 
Green sand. | 
| 
| 
Peribolaster folliculatus  . ° Pacific. 45 | 
| 
i 
1. Peribolaster folliculatus, n. sp. (Pl. LX XIIL. figs. 4-7). 
Rays five. R= 54 mm.;r=18 mm. R=3 7. Breadth of a ray at the base, 
about 20 mm.; and midway between this and the extremity about 17°5 mm., measured 
outside the spinelets. 
(ZOOL. CHALL. EXP.—PART LI,—1888.) 59 
