56 OPHIOLEPIS PAUCI8PINA. 



DescrHjjtion of a Specimen. — Diameter of disk, 5.2°°'- ; from outer 

 side of moiitli-sliield to outer corner of opposite mouth-slit, 2.2°'°*" ; width 

 of arm without spines, 1.3™'° ; length of arm, 13"""- ; distance from outer 

 side of mouth-shield to inner points of mouth-papillse, to that between 

 outer corners of mouth-slits, 1.3 : 1.1. Mouth-papilla, eleven to each 

 angle of mouth ; outermost one conical, sliar]), partly overlapping the 

 next one, which is swollen, squarish, broader than long, and the largest 

 one of any ; the rest even, close set, about as long as broad, a little 

 swollen, and more or less sharp ; innermost one pointing to centre of 

 mouth. Teeth, four ; uppermost one tapering, narrow, pointed ; the 

 rest broad, flat, even, with a curved cutting edge. Mouth-shields longer 

 than broad, bounded without by a long, ovoid curve, and wdthin by two 

 short, re-enteringly curved lines, which meet, to form an angle on the 

 middle line ; length to breadth, .7 : .5. Side mouth-shields stout, having, 

 without, a peak which runs to the inner end of the genital slit. Under 

 arm-plates with inner side curved, outer side either evenly or brokenly 

 curved, and lateral sides re-enteringly curved ; much l^roader without 

 than within, in consequence of the outer corners being prolonged late- 

 rally like ears or peaks; length to breadth (sixth plate), .4 : .6 ; first 

 plate much broader than long ; bounded without by an outer side and 

 two outer laterals, and having within a little peak which occupies the 

 outer end of the mouth-slit ; towards the end of the arm, the plates 

 have the same general form, but are more elongated, and are bounded 

 without by a very obtuse angle, and within by one which is more acute. 

 Side arm-plates conspicuous, and a good deal swollen, meeting both 

 above and below, near end of arm. Upper arm-plates much narrower 

 within than without ; four-sided ; outer side a little curved, or wavy ; 

 inner side nearly straight ; lateral sides re-enteringly curved, and sloping 

 strongly inwards towards the middle line of the arm ; length to breadth 

 (eighth plate), .4 : .7 ; towards the end of the arm the plates are nearly 

 triangular, with a point inward ; first three plates very short and rudi- 

 mentary. Supplementary pieces much wider than long, triangular, with 

 their acute angle directed downward ; they are found almost to the very 

 tip of the arm ; and, where they are largest, extend downwards nearly 

 to the upper arm-spine ; occasionally they are broken in two. In the 

 centre of the disk, above, is a conspicuous primary plate, and from this 

 there radiate ten rows of primar}' plates, two or three in each brachial 

 row, and three or four in each interbrachial row ; these plates are angu- 

 larly round and swollen, and have an average diameter of about .S"™' ; 

 in addition, there are in each interbrachial space two more radiating 

 rows of rather smaller scales, one lyiug on each side of the central row 

 of primary plates, between it and the radial shield ; all these are com- 

 pletely separated, each from its neighbor, by close single lines of little, 

 thickened, irregular scales, having an average diameter of about .2™'"-. 



