224 BULLETIN OF THE 



Peetinura rigida sp. nov. 



Special Marl*. — Very large, with cylindrical arms; disk closely granu- 

 lated and smooth. Aery small sunken radial shields; pores between under 

 arm-plates far out on arm. Nine or ten much flattened arm-spines, the 

 lowest one much the longest and largest. 



Description of a Specimen. — Diameter of disk 36 mm. Length of arm 

 175 mm. Width of arm near disk 5.5 mm. ; height 6 mm. Ten flat, close- 

 set, rough-edged mouth-papillse to each mouth-angle, of which the two 

 under the teeth are a little higher than the rest. There is also a small ad- 

 ditional papilla, nearly covered by the outermost mouth-papilla, which 

 stretches upward and embraces the second mouth-tentacle. Six short, 

 broad, Hat teeth with a curved cutting edge ; the lowest one often split in two. 

 Under arm-plates, within the disk broader than long, bounded without by 

 a curve, and within and on the sides by re-entering curves ; length to breadth 

 1.8 : 2.8. Farther out on the arm they are as broad as long, with rounded 

 corners, and they everywhere are thick and even swollen, and have pores 

 between them, nearly to the end of the arm. Side arm-plates flat, and occu- 

 pving nearly the whole height of arm. Upper arm-plates regular, not 

 broken, and with a wavy outer margin; they occupy most of the upper sur- 

 face; length to breadth 2 : 4. Mouth-shields large and lying close to the 

 mouth-papillae, roundish with a small point within, and a re-entering curve 

 without ; length to breadth 4 : 4.5. Supplementary mouth-shields small, 

 roundish, about 2 mm. in length and width. Side mouth-shields minute and 

 wedged between the first under arm-plate and the mouth-shield. Disk, ex- 

 cept small sunken radial shields about 2 mm. long, and the shields of the 

 mouth, closely and smoothly granulated with about eight grains to 1 mm. 

 Ion?;. The underlying scale-coat is of delicate, smooth scales, not more than 

 .4 mm. wide, and difficult to distinguish. Arm-spines nine or ten, much 

 flattened, about three fourths the length of the side arm-plate, except the 

 lowest, which is much stouter, and whose length equals two underarm-plates. 

 The upper spines are somewhat shorter and notably wider than the lower, 

 and all taper to a blunt point. Two tentacle-scales, of a rounded oval 

 shape ; the one which covers the base of the lowest arm-spine often larger 

 than the other. 



Color, in alcohol, purplish brown, with black radial shields. 



Variations. — Another specimen, of about tin' same size, had the lowest 

 arm-spine even longer, and often with a thickened end. 



This species stands nearest to P. seplemspinosa, from which it is distin- 

 guished by more numerous and more flattened arm-spiues, and by the great 

 length of the lowest one. 



Zanzibar; Mr. Cooke. 



