142 DR A. MILNES MARSHALL ON THE 



in the greater number and size of the spicules of the latter, which reach in the 

 tentacles a length of from 0*64 to 089 mm. and width of 0'09 to 0*12 mm. 

 The muscular layers are also far less strongly developed in the var. dura than 

 in var. mollis. 



At a later period* he described a specimen from the Atlantic at a depth of 

 690 fathoms, which was in all its characters intermediate between the two 

 other forms, and seemed to prove them to be merely varieties, and not, as once 

 supposed, specifically distinct. 



The "Triton" specimens belong clearly to the variety dura, though they 

 differ a good deal among themselves as to the size of the spicules. The single 

 specimen from the " Knight Errant " collection has much smaller spicules than 

 any of the others, and is to be referred to the variety intermedia. 



The following table gives the measurements of the " Knight Errant " speci- 

 men and of one of the typical " Triton " specimens : — 









A. 







B. 









Var. intermedia 







Var. dura 









from " Knight Errant." 







from "Triton." 



Total length, 







82 mm. 







45 mm. 



Length of rachis, 







435 







21 



„ stalk, 







38-5 (broken 



at lower 



end) 



24 



No. of polyps, . 







18 







6 



Size of spicules (largest), 



0-31 x 0-018 







0-66x011 



All the specimens of K. stelliferum were encrusted rather thickly with sand, 

 which adhered somewhat firmly to the ectoderm, and doubtless acted in part 

 as a protective envelope. The internal cavities, both stomodseum, body cavity, 

 and tentacular cavities, also contained large quantities of sand, which rendered 

 the preparation of sections a matter of some difficulty. Whether this indicates 

 a habit of retraction into the sand in which they live planted by their stalks, or 

 whether the sand is purposely swallowed for the sake of food matters that may 

 be mixed with it, I have had no opportunity of determining. 



Family 2. Umbellulidae. 



Umhellula, Lam. 



Umhellula gracilis, n. sp. (PI. XXV. figs. 29-35.) 



Specific Characters. — Distinctly bilateral. Polyps, forming a cluster on the 

 upper end of a club-shaped rachis ; greyish in colour with dark reddish-brown 

 tentacles. Stalk long, very slender and exceedingly flexible ; ending below in 

 a dilated vesicular portion. Zooids numerous on the rachis between the polyps, 



* Op. cit., p. 320. 



