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PEOCEEDINGS OP TEE NATIONAL MUSEUM 



VOL. 81 



zone. The axial region consists of much protoplasmic structure with 

 smooth styles in confusion, showing perhaps a trace of reticulation; 

 they are held together by small quantities of spongin. The peripheral 

 zone is about 400/i thick and is a dense forest of peculiar acantho- 

 styles, points out. These, as characteristic of this genus, have the 

 basal third curved and smooth, the spines very large and recurved. 

 Since most of the lamellate fronds are less than 2 mm in thickness, 

 the axial portion averages only about 700/a thick. 



Ectosomal or echinating spicules, acanthostyles (fig. 64, A, B) ; 

 size, V2,fi by 180/a to 20jii by 320/a. Interstitial spicules, smooth, ends so 

 regularly broken that it is not certain what sort they were (fig. 64, 

 E) ; size, 10/a by at least 800/a, rare, probably several millimeters long 



FiGUEB 64. — Hemcctyon Jiple de Laubenfels : A, X300; others, 

 X 100. E, fraction of total length of spicule shown 



when intact. Coring spicules, smooth styles (fig. 64, C) ; size, 15/i 

 by 430ju, to 20/x by 550ju.; also smooth strongyles (fig. 64, D) ; size, 16/^ 

 by 350/x to 19^ by 370;a. Microscleres, oxeote rhaphides (fig. 64, F) ; 

 size, 2{x by 200/i to 2/^ by 330/x. 



Rem/irhs. — The nearest relative of this form is Heniectyon hamata 

 Schmidt (1870, p. 62) from the West Indies. This, the only other 

 member of the genus, was inaccurately described by Schmidt and 

 put in the genus Raspailia. It is correctly redescribed by Topsent 

 (1920, p. 26), who erected the genus Heviectyon for it. The species 

 hyle clearly belongs in this genus, but it has many features of specific 

 difference; hmuita has a strongly reticulate axial region with much 

 spongin. Its smooth styles are smaller, only 300ju to 350/i long. Its 

 interstitial spicules are shorter than those of %Ze, being only up to 

 about 600//,. Its peripheral region had definite radiating fibers echi- 

 nated by the acanthostyles; such fibers are lacking in hyle. Its 



