1889.] NATURAL SCIENCES OF PHILADELPHIA. 143 



ON A NEW GENUS AND TWO NEW SPECIES OF OPHIURANS. 



BY J. E. IVES. 



In a collection of Ophiurans principally from the west coast of 

 North America, but also from localities in the Xorth and South 

 Pacific, recently received by the Academy from Mr. W. N. L<n king- 

 ton, there are two apparently undescribed forms, representing a new 

 genus and a new species respectively. 



They unfortunately have no locality attached to them. They are 

 described below. The figures representing the upper and lower 

 surfaces of the disk and of an arm, and the views of the side arm 

 plates near the base of an arm are enlarged two diameters. The 

 views of the outer and inner faces of an arm-bone of Ophioncus 

 granulosus have been magnified considerably (Figs. 4, 5). 



OPHIONCUS, n. g. 



Upper surface of disk covered with swollen plates and granulated ; 

 no notch in the disk over the base of the arms ; teeth few; no tooth 

 papilla? ; mouth papillae small, even, numerous ; side mouth shields 

 long, not meeting within ; arm spines, few, short, arranged on the 

 outer edge of the side arm plate ; upper and lower arm plates entire; 

 four genital openings in each interbrachial space. The genital open- 

 ings nearest to the mouth are long and narrow, and widest at their 

 inner ends ; the openings farthest from the mouth are small and 

 nearly circular. These four genital openings appear to have been 

 formed from the two usually found by the edges of each of the two 

 original slits meeting near their outer ends. I believe that Ophiura 

 is the only other genus of Ophiuridce possessing four genital openings. 

 In Ophiura, however, the inner opening is smaller than the outer one. 

 Ophioncus in general characters somewhat resembles Ophiozona, but 

 differs markedly in the swollen granulated plates of the disk and in 

 the presence of four genital openings and two tentacle scales. The 

 arm bones (figs. 4, 5) appear to have more resemblance to those of 

 Ophiozona than to those of any other genus. 



Ophioncus granulosus, n. sp. (Figs. 1-5.) 



Upper surface of disk covered with 

 irregular swollen plates, granulated ; small 

 irregularly oval, naked radial shields. 

 Lower surface of the disk covered with 

 smooth scales, granulated ; mouth shields, 

 ovate with the smaller end directed to- 



