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THE 0PHIURID7E. 



103 



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mouth papill93. The outer one is very small; the next one is the largest of 

 them all; rounded ; the next one to three are square, and finally the inner 

 one usually pointed. Sometimes there is a little median papilla below the 

 teeth; but it seems to be typical that there is no median infradental papilla. 

 The four to five teeth are broad, square, or slightly rounded. Mouth shield 

 a little wider than long, with an acute angle within and outer edge rounded. 

 The inner sides are re-enteringly curved, lateral sides straight, outer corners 

 rounded. Side mouth shields very short and broad, meeting within; their 

 outer end much broader than the inner end. 



First ventral plate very small, regularly five-sided, wdth an angle inward. 

 Those beyond a little longer than broad, in mutual contact to the fifth or 

 sixth joint, farther off widely separated by the side arm-plates. The second 

 to sixth have their inner angle truncated, the piece in contact rapidly 

 diminishing in width; those beyond the sixth have an acute angle within. 

 The outer side in the first one or two plates is limited by three straight lines, 

 meeting under obtuse angles; farther off there are only two straight lines, 

 which make an obtuse angle in the median line ; sometimes the outer edge is 

 more rounded. The lateral sides are restricted on the middle by the tentacle 

 pores; inner part re-enteringly curved, outer straight, so directed as to mate 

 an acute angle with the longitudinal axis of the arm. Side arm-plates with 

 the sides curved, outer edge rather thick and prominent, rounded ; on the 

 three joints in the disk they are wholly straight, outer edge not thickened. 

 Dorsal plates almost rhomboidal. The three to four inner ones are in mutual 

 contact, and have thus their inner angle truncated ; from the fourth or fifth 

 they are separated by the side arm-plates, and have an acute angle within ; 

 all the sides are a little rounded. They are rather thick and high, as wide 

 as long. The first dorsal plate has the outer edge much rounded, and is 

 much broader than long. Inside that there is a little plate, which may be con- 

 sidered as a rudimentary dorsal plate; it is in contact with the outer one of 

 that series of scales which separates the radial shields. At the base of the 

 arm there is on each side one rather large and a few small scales. The arm 

 is not very high, oval in cross section. The joints are somewhat nodose^ 

 constricted at their inner, thickened at their outer end. 



The disk is covered wath large, flat, partly overhapping scales, among 

 which only a few small ones are seen. The primary plates are very con- 

 spicuous. The central plate is five-sided with an angle to each radius, each 

 side joined by an elongated, rounded scale. The radial shields widely sepa- 



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