ECHINOIDEA. I. 



77 



between two kinds of tridentate pedicellarise. The neck is rather short, the stalk of the common 

 structure (PL XIV. Fig. 31). The cover-plate of the triphyllous pedicellariae is rather well developed, 

 with numerous small holes; the outer part of the blade is not very broad, the edge finely serrate 

 (PL XII. Fig. 16). 



The spicules of the tube feet on the actinal side are large, generally somewhat curved fenes- 

 trated plates (PI. XIV. Fig. 4a); they inclose the foot completely and are not distinctly arranged in 

 longitudinal series. A little sucking disk is found with a rather irregular calcareous rosette (PL XIV. 

 Fig. 4). Just below the sucking disk the spicules stick, so that this part of the tube foot cannot 

 be contracted, whereas the other part is highly contractible, as is commonly the case in the Echinids; 

 the point with the sucking disk is then seen to be sharply marked off from the other, much thicker 

 part of the tube foot. In the contracted part the spicules are arranged in such a way as to form an 

 imbrication. The tube feet of the abactinal side have, as usual, no sucking disk, and the spicules are 

 small, irregular, branched calcareous bodies (PL XIV. Fig. 4 a), arranged in 2—3 longitudinal series. 



The sphseridias are as usual placed along the tube feet quite up on the abactinal side, where 

 they are situated at the large tube foot, 1 — 3 spheeridice at each foot. They are rather lengthened 

 (PL XIV. Fig. n). 



Together with this specimen a beautiful, small one has been taken, as mentioned above, of a 

 diameter of 27 mni , which I suppose will have to be referred to the same species, although it differs 

 somewhat from the large specimen with regard to the structure of the test (PL IV. Figs. 4, 5). The 

 ambulacral areas are somewhat narrower than the interambulacral ones, also on the actinal side. The 

 tube feet are placed in three series, but not very far from each other; they are arranged in arcs of 

 three as in an Echinus, which is especially distinctly seen on the abactinal side. The small ambula- 

 cral plates are not distinct, the primary ones are especially regular and straight; this applies also to 

 the interambulacral plates, which are, accordingly, not yet angularly bent as in the adult. The primary 

 spines and tubercles form rather regular series in both areas; in the ambulacral areas there are on 

 the actinal side a couple of especially large ones near the ambitus, much larger than the adjoining 

 ones; in some plates spines are quite wanting. In the interambulacral areas they form a more regular 

 series on either side gradually increasing in size towards the ambitus; primary tubercles are found in 

 all the plates, and some have, besides, a few secondary tubercles. On the abactinal side the series of 

 tubercles are very regular in the ambulacral areas where the size is about the same till towards the 

 apical area. The tubercles of the interambulacral areas are more unequal, some being quite small, 

 others very large. The spines, unfortunately, are all broken. The apical area is large, the madre- 

 porite rather distinct. No genital papillae are as yet developed, nor are the pores as yet formed. 

 The pedicellariae are as in the large specimen, but as yet no large tridentate pedicellarise with the blade 

 filled by a thorny net of meshes are found. Of the tube feet on the abactinal side only the innermost 

 one of each arc is well developed, the two others are rudimentary as in the large specimen. The 

 spicules of the tube feet of the actinal side are as those of the large specimen, only somewhat smaller 

 and distinctly arranged in series. The sucking disk only slightly developed. In the abactinal tube 

 feet the spicules have only just begun to appear. 



Sperosoma Grimaldii was hitherto only known from the Azores, from c. 600—930 fathoms. As 



