356 s. GOTO : 



are evidently not constant, can be more easily seen on a denuded 

 specimen, in which they are marked by a small pore for each. 



Adambulacrals. — The first adambnlacral plates are not very 

 conspicuously différent in form from the rest. The adambulacral 

 armature consists of three rows, and may be shown by the formula 

 5 (6)-(3) 4-3 (PI. IX, fig. 148), The first row is very conspicuous 

 and mostly consists of five subequal, almost straight, stout, 

 prismatic spines with blunt ends, slightly flattened in a direction 

 transverse to the ambulacra! furrow. This series may consist of six 

 spines on some of the plates. There is a well marked furrow 

 between the first and the second row. The second row usually 

 consists of four spines, similar in form to those of the first, but 

 slightly shorter, and almost as conspicuous as the latter. The 

 third row usually consists of three spines of a pyramidal shape, 

 similar to those of the ventrolateral plates. Occasionally the last 

 row contains four spines ; and on the first adambulacral plate 

 there may be a fourth row of two to four spines. 



Mouth-jjlafes. — Each mouth-plate is elongated-triangular and 

 is apposed to its fellow by the longest side. There are eight or 

 nine spines on the furrow border in the larger specimen, but only 

 seven in the smaller. In the larger specimen they are very 

 stout and conspicuous, and flattened transversely to the furrow, 

 the spine at the mouth end being exactly similar in shape and 

 length to the others. In the smaller specimen the corresponding 

 spines are more slender and the one at the mouth end is notice- 

 ably stouter than the others ; they are also nearly cylindrical in 

 form. In both specimens, the spine at the abcentral end of this 

 row is stouter than the others. On the side facing the first 

 adambulacral plate there are four or five spines, of which the 



