OPHIOZONA TACIFICA. 67 



Ophiozona pacifica Lyman. 



Ophiolrpis pnrlfirnJjVTKK'S. Vidensk. Medilelelsor. Jan., 1856. 

 Ophiolepis pacijica Lutkex. AcUlit. ad Hist. Oph., p. 104. 



Sjoecial Marks. — Arms three or four times the diameter of the disk. 

 Arm-spines fom- or five, very small, and of even length. 



Description of a Sjyecimen. — Diameter of disk, 4.7"""-; from outer 

 side of moutli-shields to outer corner of opposite mouth-slits, 2.3"""' ; 

 width of ami without spines, LI""™ ; length of arm, 18"""-; distance from 

 outer side of mouth-shield to inner points of mouth-papilliB, to that 

 between outer corners of mouth-slits, 1.1 : 1. Mouth-papilla), eleven to 

 each angle of mouth, small, close set, flat, angular, squarish ; outermost 

 one somewhat pointed, and slightly overlapping its next neighbor, 

 which is much the largest of all. Teeth four, Hat, broad, with a curved 

 cutting edge ; uppermost one narrowest. Mouth-shields much longer 

 than broad, bounded by an ovoid curve without, and by an angle within ; 

 length to breadth, .6 : .4. Side mouth-shields sw^ollen, triangular, large ; 

 running out, with one corner, to the head of the genital sht. Under 

 arm-plates broader than long, broader Avithout than within ; outer and 

 inner sides strongly re-enteringly curved ; length to breadth (sixth 

 plate), .4 : .6 ; first plate nearly oval, as broad as the following plates, 

 with a projection within filling the outer end of the genital slit ; at the 

 tip of the arm the plates are sharp wedge-shaped. Side arm-plates 

 occupying a good deal of upper and under surface, but not meeting 

 above and below till about two thirds out on the arm. Upper arm- 

 plates very regular, a good deal broader without than within, four-sided, 

 the sides almost perfectly straight; length to breadth (sixth plate), 

 .4 : .8 ; the notches in the disk are so shallow that only one rudimentary 

 plate is admitted. In the centre of the disk, above, is a large, nearly 

 round, primary plate, .6"""' in diameter, surrounded by five little trian- 

 gular scales ; outside these is a circle of five large oval plates, one in 

 each brachial space ; the interbrachial spaces have three radiating rows 

 of plates, those of the central row being the largest ; there are also a 

 few very small scales scattered among the others. Radial shields 

 sunken, irregular, longer than broad, running to the edge of the disk, 

 separated by a single row of three scales ; their outer ends bounded by 

 two large, narrow, curved scales ; length to breadth, .9 : .6. Interbra- 

 chial spaces, below, covered with nearly equal scales, with some little 

 ones among them ; genital slits bordered by three narrow scales, of 

 which the outer one is longest and widest. Arm-spines four, very 

 small, of even length, cylindrical, tapering, about one third as long as 



