SHALLOW-WATER STARFISHES 79 



On the medium-sized specimens the pentagon of the disk is very 

 evident, but in large specimens it is obscured by the numerous inter- 

 polated scattered spines. In those about six to eight inches in 

 diameter, the central plate, five radial, and five interradial primary 

 plates are evident. Each bears a cluster, usually of four to six short, 

 thick, clavate spines, with ovate or acorn-shaped striated tips. They 

 are similar, in size and form, to those of the median radial rows. 



Other somewhat smaller, but similar, spines are scattered within 

 and around the primary pentagon, and over the dorsal surface gen- 

 erally. But the dorsal spines are not numerous in the young. They 

 do not form distinct rows, but are irregularly scattered, and are 

 mostly pretty nearly equal in size and form. In the larger specimen, 

 ten to twelve inches in diameter, the dorsal spines become decidedly 

 more numerous, and many are grouped two to four or more on one 



plate. 



The superomarginal spines are similar to the dorsals, usually with 

 rather more conical tips, which are strongly striated. They form a 

 regular, close row, simple in the smaller specimens, but often double 

 proximally in the larger ones. 



The inferomarginal row is very regular and nearly always double, 

 two spines standing obliquely on each plate, sometimes three in the 

 larger specimens. They are rather stouter and more obtuse than the 

 upper marginals, usually with the tips striated in small specimens; 

 but in the larger ones these spines mostly lose their striations, and 

 many become more or less flattened distally, while some are apt to 

 have a distal furrow on the upper side ("gouge-shaped"), though 

 this is by no means constant. 



In nearly all the specimens there are but two simple, regular 

 actinal rows of spines, making, with the inferomarginals, four close, 

 unusually regular rows. The actinals are short and stout, similar 

 to the inferomarginals. In the larger specimens some of them are 

 somewhat flattened, and some are often grooved or slightly bilobed 

 distally. 



The adambulacral spines are slender, four or sometimes five corre- 

 sponding to each synactinal plate. In young examples they are 

 mostly regularly tapered and form a very regular even row ; in the 

 larger ones, many of them are often stouter, obtuse, cylindric, a 

 little flattened, or even slightly clavate. They become longer proxi- 

 mally, near the mouth. 



Major pedicellarise of rather large size occur on the back, sides, 

 and interradial axils, on the adambulacral spines, and on the inner 



