114 the apodous holothubians 



Key to the Species of Chiiudota. 



A. — Wheel-iJapilliB numerous, more or less uniformly scattered all over the body, with no 

 evident arrangement in longitudinal series; digits 8-14. (In young specimens, pa- 

 pillEe may be very I'ew on ventral side.) 

 B. — Numerous curved rods (plate vii, iig. 2?), with more or less branched ends scat- 

 tered all over interambulacra kotifera 



BB. — No such rods in interambulacra. 



Miliary granules of longitudinal muscles, minute oval particles; polian vessels 



5-10 FERNANDENSIS 



Jliliary granules of radii longer than diameter of wheels; polian vessels 15-20. 



STUHLMANNI 



.1/1. — Wheel-papillie numerous or few, confined to interambulacra, and there forming more or 

 less irregular longitudinal series, less abundant on ventral side and often wholly 

 wanting there. 

 B. — Digits of tentacles about 20; wheel-papilla,' in 5 irregular series; numerous minute 



crescent-shaped bodies in skin violacea 



HB. — Digits of tentacles generally fewer than 1(5 (very rarely 18). 



C. — Wheel-papillae very few and only in right and left dorsal interambulacra : stel- 

 late, perforated plates (plate vii. fig. 25) in skin mabenzfxleri 



CO. — No stellate plates in skin. 



D. — Numerous "buttons" ("schnallenformiger Hautkalkkorper") in skin; 



wheel-papillae in 5 simple longitudinal series eximia 



DV.—'So "buttons" in skin. 



E. — Curved rods, with enlarged ends (plate vii, figs. 16 and 27), which 

 may be smooth or spinous, or even branched, scattered in skin, 

 at least along ambulacra. 

 F. — Size large, up to 200 mm. ; color more or less purple ; wheel- 

 papillae confined almost wholly to mid-dorsal interambulacrum. 

 Curved rods very small (40-60 /t), confined to ambulacra, 



and distinctly curved kegalis 



Curved rods larger (80-120 m), uniformly scattered, and 



commonly almost straight uniserialis 



FF. — Size small, under 100 mm.; color not purple; wheel-papilla; and 



rods more or less generally present in all the interambulacra. 



Color red or reddish; wheel-papillffi numerous dorsally; 



occurs about coral reefs rigida 



Color whitish; wheel-papilla' in an irregular single row in 

 each interambulacrum : occurs in mangrove swamps. 



INTERMEDIA 



l'!E. — No such curved rods in skin. 



F. — Size small, usually under 100 mm. (rarely twii-e that) ; color in 

 life yellowish, pink, red or purple, becoming whitish, grayish, 

 yellowish, dusky or purplish red in alcohol ; wheel-papilliE, of 

 course, white. 



Wheel-])apillnn very large, 1-1.5 mm. in diameter; polian ves- 

 sels few, only 4-5 ; austral plsanii 



Wheel-papillae smaller and polian vessels numerous, 10-20 or 



more : boreal l.^Jvis 



FF. — Size largo, up to ."00 mm.; crdor prevailingly grayish, with more 

 or less red pigment in skin discolor 



