REPORT ON THE ASTEROLDEA. 



377 



Chorology of the Genus Cycethra. 



a. Geographical distribution : — 



Atlantic : Three species between the parallels of 45° and 55° S. 



Cycethra pinguis and Cycethra nitida, off Cape Virgins, near the 

 Atlantic entrance to the Strait of Magellan. Cycethra electilis, off 

 the Falkland Islands. 



Pacific : One species between the parallels of 45° and 55° S. 



Cycethra simplex, in the Trinidad Channel, west coast of Patagonia. 



/3. Bathymetrical range: 12 to 55 fathoms. 



<y. Nature of the Sea-bottom : All the species inhabit a sandy bottom. 



Clwrological Synopsis of the Species. 



1. Cycethra electilis, n. sp. (PI. LX. figs. 3 and 4 ; PI. LXIL figs. 2 and 3). 



Eays five. K = 40 mm. ; r = 16 mm. R = 2 - 5 r. Breadth of a ray between the third 

 and fourth infero-marginal plates, 15 mm. 



Rays moderately produced and comparatively flat, broadest at the base, and tapering 

 gradually therefrom to the extremity, which is rather broad and obtusely rounded. Disk 

 capable of slight inflation, which may be emphasised by a faint depression in the median 

 interradial line. Margin moderately thick and vertical. Interbrachial arcs more or less 

 rounded. Actinal surface plane. 



The abactinal area is covered with small plates which bear small paxilliform groups of 

 spines. These are composed of from three to seven short, cylindrical, obtusely-rounded, 

 equal spinelets, which are erect and covered with membrane, the latter forming a compact 

 fleshy mass within the paxilla in which the spinelets are imbedded. Large and smaller 

 paxillse are intermixed, but the difference in size is not conspicuous at first sight, and no 

 order of arrangement is discernible ; they are distinctly spaced. Numerous papulae are 

 present in the interspaces, sometimes two or three together. 



The marginal plates are small and confined entirely to the margin, occupying the 



(ZOOL. CHALL. ESP. PART IX 1S88.) 48 



