I9I3-] T. L. BoMFOKD : O-phiuroids in the Indian Museum. 223 



The upper surface of the disc was even, and not elevated 

 above the level of the upper surface of the arms : since its immer- 

 sion in spirit the soft parts have somewhat collapsed in the centre 

 (as can be seen in plate xiii, fig. 4), and the radial shields of the 

 disc, and the lateral arm plates also, are now clearly distinguishable 



I have been able to compare this specimen with an example 

 of r. palmiferus -{Lam.) (Regd. no. zev ^) presented to the 

 Museum many years ago by Dr. Hungerford, who obtained it in 

 Hong Kong. 



The following features serve to distinguish the two 



species : — 



(i) In comparison with the size of the disc, the inter-brachial 



spaces in T. elegans are'much wider than in T. palmiferus ; 



or, in other words, the arms at their bases are narrower. 

 (2) The arms of T. elegans are much more slender : not only 



Trichaster elegans, x 107. 



Fig. 3. 



Trichaster palmiferus, x 107. 



are they relatively narrow at their bases, but at the 

 first bifurcation their breadth has diminished to less than 

 one fourth part, while in T. palmiferus the breadth at 

 this point is one third of the breadth at the base of the 

 arms. 



(3) The apertures of the genital bursae are much more widely 



separated in T. elegans. In the specimen of T. palmi- 

 ferus from Hong Kong, the two apertures in each 

 inter-brachial space practically unite to form one and 

 the surface that should intervene is drawn in, and 

 forms an almost linear septum. This difference, which 

 is illustrated in plate xiii, figs. 2 and 3, is the conse- 

 quence of the reduced size of the inter-brachial space. 



(4) The radial shields on the disc, at their outer end, and the 



lateral arm plates, at their upper ends, are only slightly 

 expanded : the latter nowhere form conical elevations. 



