256 H. N. MOSELET. 



The radial annularia are roughly triangular in form, with broad 

 bases shaped angularly, so as to fit in between the pharyngealia^ 

 which succeed them posteriorly, and elongated apices. These 

 apices are at their tips deeply notched, probably, as in other 

 forms, for the passage of the radial canals of the water vas- 

 cular system, and the bodies of the plates themselves are per- 

 forated, each by an oval apei'ture, possibly for the exit of nerves, 

 as in Synapta and Echinosoma but very possibly, also, for the 

 attachment of the retractor muscles of the pharynx. In Hap- 

 lodactyla there ai'e depressions on the radial annularia for these 

 muscles.^ Or the apertures may represent the bifurcations at 

 the bases of the radial annularia of Holothuria princeps 

 and other species, which are believed by Semper to be the homo- 

 logues of the radial pliaryngealia of certain Dendrochirotse. The 

 median ventral radial annulare is much smaller than the others; 

 is not perforated nor notched at its apex, and it is partially fused 

 laterally with the adjacent interradial annularia. The retractor 

 muscle attached to it is very probably smaller than those in- 

 serted into the other four radials. The interradial annularia 

 are longer and broader than the radial, but of a similar tri- 

 angular shape. They are not perforated or notched. The two 

 ventral interradials are differently formed from the others, being 

 un symmetrical and pushed inwards towards the ventral middle 

 line, so that the intervals between their anterior processes and 

 that of the ventral radial annulare are much narrower than 

 the remaining corresponding intervals. Opposite these minor 

 ventral intervals internally are attached the two tentacles out 

 of the ten present, which, as in many other Dendrochirotse, are 

 much smaller than the rest. Opposite the remaining correspond- 

 ing intervals are attached the eight larger tentacles. All the 

 tentacles are dendritic (Fig. 2), and placed opposite the intervals 

 between the radii and interradii. They have no ampullae. 

 Behind each of the annularia follows a double row of well- 

 defined calcareous plates (pharyngealia), and the ten double rows 

 of these being closely ^united, side by side, invest the walls of the 

 pharynx with a continuous calcareous armour. I term these 

 1 See Semper, ' Reisen in den Pliillipinen. Holotliurien,' S. 160. 



