144 Mr. Forbes on the Radiata of the Eastern Mediterranean. 



accessory plate at its upper margin, but neither of the plates encroaches on 

 the parts of the body which form the triangular spaces between the rays. The 

 space between the ovarian plates and the little comb of spines which guards 

 the mouth is covered with granules like those which cover the body. The co- 

 lour when recent was grayish, in the dried specimen yellowish. 



On this specimen alone I should scarcely have ventured to found a genus, 

 remarkable as are its characters, but would rather have referred it for the 

 present to the genus Ophiocoma, as an aberrant form approaching Ophiura; 

 but I have had an opportunity of examining a large foreign species, which 

 shows that it has rather a closer affinity with Ophiura than Ophiocoma, and in 

 fact belongs to a distinct and well-marked genus, differing from the former 

 in having the discs clothed with granules, in the absence of the pectinated 

 scales embracing the origin of the rays, and in the ovarian plates (not sol- 

 dered as in Ophiura into one) not encroaching on the body. From Ophio- 

 coma it is distinguished by the lateral ray plates lapping over each other and 

 the posterior ray plates, as in Ophiura, and instead of bearing the spines on a 

 transverse ridge or keel, having them articulated to their superior margins, so 

 that when the animal is dead they lie close to the rays, and do not bristle out 

 as in Ophiocoma. As among the species of Ophiura, the twin plates of the 

 disc opposite the origin of each ray, have a generic and not a specific value. 

 The sources of essential specific character, judging from the species before me, 

 are 1st, the form of the superior ray-scales ; 2nd, the number of spines on the 

 lateral ray-scales ; 3rd, the form of the upper surface of the rays ; and 4th, 

 the form of the disc. The habit of the genus is that of Ophiura. Judging 

 from analogy, the suckers, when observed, will be found to be simple and not 

 pinnate or dentate. I now add the definition of the genus, and the specific 

 character of the Mediterranean species. 



Genus Pectinura, Forbes. 



Corpus orbiculare, squamosum, granulosum, ad peripheriam radiatum: radiis simplicibus, 

 squamosis, in corporis discum sub-prolongatis ; squamis radiorum lateralibus adpressis, 

 in marginibus superioribus spiniferis: ossiculis ovarialibus binis, in corporis lobos non 

 productis. 



