ECHINARACHNIUS PARMA. 317 



tinguish the species established by Michelin and Gray, based upon slight 

 local differences, such as the outline of the test from above or in profile, the 

 more or less open petaloid ambulacra, the distinctness of the branches of 

 the ambulacral furrows, which are all features subject to great variation in 

 specimens from the same locality. The length of the petals is very vari- 

 able, in some specimens not extending beyond half-way from apex to 

 margin, while in others they reach fully two thirds of the distance. There 

 are two principal branches of the ambulacral furrows, commencing from two 

 thirds the distance of the mouth to the edge of the test. 



Littoral to 40 fathoms. 



Young specimens of Echiuarachnius parma, measuring from 2.1 mm to 

 g 2mm. j n di ame ter, are readily found in the stomach of our cod. The out- 

 line of the youngest specimen observed is elliptical (PI. XII. f. l). The test 

 is high, arched, resembling somewhat a Cassidulus from the position of the 

 anus (PI. XII. f. 3), and an Echinometra from the vertical rows of large 

 tubercles, one for each ambulacral and interambulacral plate, forming regu- 

 larly decreasing rows from the apex to the mouth. The lower surface is 

 nearly flat, the actinostome is large, pentagonal (PL XII f. 2), being fully 

 one third the diameter of the test across the opening. There are but slight 

 traces here and there of miliaries ; the tubercles are so closely crowded that 

 it is impossible, beyond the presence of five pairs of pores, one pair for each 

 ambulacrum, to detect any further trace of the ambulacral pores, although it 

 is easy to identify the ambulacral rows. The vent is placed a short distance 

 above the ambitus (PL XII. J. 3), no trace of the poriferous zone could be 

 seen near the mouth. The rotules are present in shape of a peculiar spine, 

 which is most prominent in specimens measuring about 4. mm in longitudinal 

 diameter. In a somewhat older specimen the difference of outline is very 

 striking; it is pear-shaped (PI. XII f. 4), the blunt end being the posterior; 

 the test is still considerably arched, but has become a good deal flattened 

 when compared to the previous stage. We find also the commencement of 

 the difference in the arrangement of the ambulacral and interambulacral 

 plates, due to the different rate of growth of the two areas. The mouth is 



