262 MB. "W. PET!CT SLADETsT OlS" THE 



flattened, accompanied by a second spine, about two thirds the 

 length of the marginal spine, placed immediately behind and close 

 to the aboral side of the plate. Two or three small compressed 

 spinelets are situated in line on the aboral side of the plate, that 

 near the inner extremity adjacent to the adambulaeral plates 

 often slightly largest. No other spines are present on the infero- 

 marginal plates, which are covered with moderately well-spaced 

 squamules. 



Ambulacral spines forming three series on the inner part of the 

 ray, but become reduced to two on the outer portion. The inner 

 series consists of three spinelets, which are rather short, the middle 

 one delicate and clavate at the extremity, and two lateral compa- 

 nions rather shorter, flat and obtuse. The second series consists of 

 two or three spinelets shorter than the inner series and more or 

 less flattened and truncate. When a third spinelet is present it is 

 very frequently placed somewhat behind the other two, opposite 

 their interspace ; and might almost be counted with the third series, 

 which latter may consist of only two or three small cilia-like 

 spines or of four flat modified spines forming a well- developed 

 pedicellaria. These organs are irregular in their occurrence and 

 are only present on the inner half of the ray ; on the outer part 

 of the ray the third series of ambulacral spines is apparently 

 wanting altogether. The pedicellarise are large and conspicuous, 

 and four or five are present along each side of a furrow, usually 

 on alternate plates ; all are uniform and with four valves, regu- 

 larly apposed two and two, the spinelets which form the valves 

 being more or less flattened and arched, and terminate in an 

 abruptly pointed or lanceolate extremity. Ventral plates very 

 few ; the two immediately behind the mouth-plates each bear a 

 large pedicellaria similar to those just mentioned. 



Mouth-plates elongate and narrow, with a single line of com- 

 paratively long and robust spinelets along their superficies, cylin- 

 drical or slightly compressed and obtuse ; all nearly uniform in 

 size excepting the innermost one or two, which are somewhat 

 larger than the others. 



Paxillse of the dorsal area large, having 1-4, or even more, 

 central spiniform granules on the tabulum, surrounded by 8-12 

 short spinelets in a circle on the periphery. A slight prominence 

 is present in the centre of the disk of some examples, but scarcely 

 sufficient to produce a conical peak. In one specimen a slight 

 invagination occurs in the centre of the prominence. 



