194 



and the arms shorter ; the color also must be quite distinct. A, 

 7?iicrodiscus has, even in small si3ecimens, the upper arm-plates 

 touching each other and twice as broad as long. A. tenera has 

 upper and lower arm-plates and mouth-shields of a different form. 

 A. squamata has dilFerently shaped mouth-shields and much 

 shorter arms. A, tenuis stands very near the present species ; 

 but the arms, in specimens of the same size, are not more than 

 half as long. 



Locality, Puget Sound. Dr. Kennerly. 



Smithsonian Institution, Nos. 1037, 1053, 1057. 



Amphiura occidentalism (Lyman,) sp. nov. 



Description of a Specimen. Diameter of disc, 5.8 millim. 

 Outer edge of mouth-shield to outer corner of opposite mouth- 

 slit, 2.2 millim. Greatest width of arm, without spines, 1.3 mil- 

 lim. As the arms were somewhat broken, their length could not 

 well be measured ; but, from their proportions, they must have 

 been at least eight times the diameter of the disc. Mouth-papil- 

 lae rounded ; innermost one stoutest, and pointing to centre of 

 mouth. Mouth-shields small, oval diamond-shaped, the angles 

 being so rounded as to give almost a true oval ; outer angle mak- 

 ing a very slight peak ; length to breadth, .4 : .5. Side mouth- 

 shields not meeting within. Under arm-plates square oblong j 

 angles somewhat rounded ; outer side with a slightly reentering 

 curve ; 2d plate differs from the rest, being five-sided, with its 

 fifth angle directed inward ; it is separated from the rudimentary 

 1st plate, by narrow prolongations of the side arm-plates. The 

 next three or four plates are in like manner separated, while those 

 further out on the arm are close together, which is an inversion 

 of the usual order. Length of plates to breadth, .4 : .4. Upper 

 arm-plates oblong, with rounded corners ; outer side with a 

 slightly reentering curve; length to breadth, .5:1. Scales of disc 

 fine, smooth, and even, above and below ; primary plates distin- 

 guished by greater size. Arm-spines 3, not tapering, rather 

 stout, rounded at the end, flattened, about as long as the joints. 

 Two small, rounded tentacle-scales. Color, in alcohol : disc, above, 

 faint greenish gray ; arms and under surface, straw-color. 



Variations. The mouth-shields may be quite oval ; the 2d 

 under arm-plate, instead of being five-sided, may resemble the 

 rest. 



