MUSEUxM OF COMPARATIVE ZOOLOGY. 155 



side thorns. It is to be noticed that the size and shape of the tentacle-scale, 

 when specimens of the same size are compared, give a pretty constant character 

 in Ophiacantha and Ophiomitra. 

 Station 87, 1675 fathoms, 2 specimens. 



Ophiomitra dipsacos sp. nov. 



Plate Vin. Figs. 213-215. 



Special Marks. — Upper arm-spmes long and slender, marginal disk-plates 

 large and swollen ; central disk-scales fine, and bearing minute thorny stumps ; 

 arm wide. 



Description of an Individual (Station 24), — - Diameter of disk 10 mm. Width 

 of arm without si^ines 3.4 mm. Mouth-papilLx nine to eleven to each angle, 

 whereof the innermost odd one is. flat spearhead-shaped ; and the two outer 

 ones on each side are ill-defined, being sometimes small papillae, or again 

 forming a ^ort of curled sheath to the mouth-tentacle ; the other papilla3 are 

 pointed and flattened. Mouth-shields as long as broad, small, having an 

 obtuse angle within, and a truncated angle or a deep curve without ; 

 outer edge often a little curled ; length to breadth 2 : 2, Side mouth- 

 shields wide, with outer side strongly curved. Under arm-plates, near 

 base of arm, large, much wider than long, -with an outer edge gently curved 

 and slightly thickened, and reaching nearly across the arm ; lateral sides 

 re-enteringly curved, with a peak within, where each plate is separated from 

 its neighbor by the side arm-plates. Upper arm-plates slightly swollen, 

 bounded without by a gentle curve, and within by a deep curve or truncated 

 angle ; they are separated by side arm-plates, which are prominent, and meet 

 freely above and below. Disk thick and puff"ed, rising well above the arms, 

 with a constriction and furrow in each interbrachial space. The area between 

 this constriction and the radial shields, on either side, is occupied by four trans- 

 verse plates running diagonally inward, and outside these is a similar larger 

 plate forming the margin of the disk. Central disk covered with fine over- 

 lapping scales, eight or ten on a line between central point and inner angle of 

 radial shield ; they are sparsely beset with minute stumps bearing a crown of 

 thorns. On the disk margin, over each arm, a few small grains or stumps. 

 Eadial shields of a wide pear-seed shape, with an angle inward, nearly or quite 

 joined without ; separated within by a broad wedge of scales ; length to 

 breadth 2.8 : 1.7. Near base of arm six strongly thorny, glassy, cylindrical 

 arm-spines, whereof the two upper ones are very long, slender, and tapering, 

 and the lowest is thick and l)lunt ; lengths to that of an arm-joint 5, 7, 3.5, 2.5, 

 2, 1.8 : 1.3. Two large pointed tentacle-scales on first pore ; one on each of 

 those beyond ; toward middle of arm, the scales are more elongated and pointed, 

 and have one or two microscopic thorns. Color in alcohol, very pale brown. 

 Station 24, 390 fathoms, 1 specimen. 



