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PROCEEDINGS OF THE NATIONAL MUSEUM. 



VOL. 54. 



triradiates in two sorts and of quadriradiates, all which spicules 

 are disposed parallel to the gastral surface. The gastral surface is 

 covered with microxea occurring irregularly, but moderately densely 

 together. 



/Spicules. — Dermal triradiates in part {a) regular or subregular, 

 very large though variable in size; rays nearly straight, tapering 

 from base to sharp point, 190-900/x long and 28-100/* thick at base. 

 Other dermal triradiates (b) sagittal, slender; rays nearly equally 

 thick, not lying in one plane. Basal ray straight, usually slightly 

 longer than paired rays, 110-250pL long and 8-20[ji. thick at base. 

 Paired rays gently curved forewards, 80-210[x long and 8-20[jl thick 

 at base. 



Triradiates of chamber layer regular or subregular, variable in 

 size; similar to those of dermal skeleton. 



Fig. 9. — Leucandra foliata. a, regular dermal triradiate. b, sagittal dermal 



TRIRADIATES. C, QUADRIRADIATES OF THE LARGER ESHALANT CANAL. d, GASTRAL TRI- 

 RADIATE. e, GASTRAL QUADRIRADIATES. f, MICROXEA. O-e^ X 100 ; f, X 400. 



Quadriradiates of the larger exhalant canals (c) sagittal, slender. 

 Basal ray straight, usually longer, but sometimes shorter than paired 

 rays, not 'lying in the plane of paired rays. Paired rays curved, 

 sometimes more or less crooked, usually slightly broader than basal 

 ray, 150-200/a long and 12-16/* thick at base. Apical ray very slender, 

 more or less curved, finely pointed, measuring up to 100/* long and 

 12/i, thick at base. 



Gastral triradiates regular or subregular, large; similar to those 

 of dermal skeleton and of chamber layer. 



The smaller gastral tiradiates (d) strongly sagittal, exactly like 

 gastral quadriradiates except in the absence of apical ray. 



Gastral quadriradiates (e) strongly sagittal, with basal ray 

 straight, much shorter and slightly thinner than paired rays, 80-210/i 

 long and 12-16/* thick at base. Paired rays doubly slightly curved, 



