342 BULLETIN OF THE 



Amphiura; by its spinous disk and rough spines, to Ophiacantha and 

 Ophiomitra. 



Ophiothamnus vicarius* Lyman, sp. nov. 



Special Mints. — Disk beset with numerous slender spines. Seven or 

 eight arm-spines; the upper ones longest, and all slender and tapering. 

 Seven inouth-papillse. 



Description of a Specimen. — Diameter of disk 3.5 mm. Length of arm 

 20 mm. Mouth-papillae, seven to eaeh angle, whereof the innermost one 

 stands immediately below the teeth, and is just like them; of the three 

 papilla: on eaeh side, the two inner ones are together about as broad as the 

 outer one. The seven make an even, crowded row, and are all stout. Teeth 

 four, short, broad, flat, with the cutting edge slightly curved, the upper- 

 most one thinnest. Mouth-shields small, .3 mm. long, pointed within, a little 

 curved -without, making a sort of heart-shape ; they are closely wedged into 

 the angle formed by the union of the s'de mouth-shields. Side mouth- 

 shields large and strong, .5 mm. long, meeting within, and extending well 

 outside the mouth-shield proper ; they bear the outer wide mouth-papilla;, 

 while the other mouth-papillae are attached to the mouth-frames, except the 

 central innermost one, which grows on the jaw itself. Under arm-plates 

 wider without than within ; outer side curved slightly, laterals encroached 

 upon by the tentacle scales; inner side making a small peak or angle; 

 length (4th joint), .3 mm. The first underarm-plate is oblong, and tightly 

 pressed between the bases of the side mouth-shields. Side arm-plates large, 

 and rather prominent, meeting above and below ; their line of juncture 

 below is about half as long as the under arm-plate. Upper arm-plates, 

 .3 mm. long : outer side cleanly curved, and nearly as wide as the arm : within 

 they are bounded by outer curves of the preceding side arm-plates, which 

 give them the appearance of having a peak. Disk beset, above and below, 

 with long slender spines, which arc more numerous on the upper surface, 

 where their length is ..'> mm., while, in the lower interbraehial spaces, the 

 longest are ,3 mm. In a dry specimen, tie somewhat coarse and irregular 

 scaling of the disk is everywhere visible. Radial shields, roughly semicir- 

 cular, so that, together they make a round figure: their outline, however, 

 is not regular, and they have a slight swelling at their outer point; they 

 touch eaeh other near the disk margin ; but, within, are separated by one, 

 anl sometimes by two, large scales; en their edges they often have two or 

 thn e spines. Ann-spines slender, rounded, gradually tapering, sharp, all 

 similar in shape, upper ones longest ; close to the disk they are much lon- 

 ger than just beyond; fourth joint, eight spines, whose lengths are, to that 



• s i cnlli d becau-c it seems to replace the common Ophiothrix of the shallower 



