52 THE VOYAGE OF H.M.S. CHALLENGER. 



regular as that of the gastric openings of the radial tubes. The internal structure can be 

 seen on PI. VI. fig. la, but it must be noticed that, occasionally, the exhalent canals, like 

 those in Leucilla uter, n. sp., give origin to secondary lateral invaginations. 



Skeleton. — The skeleton consists of gastric triradiate, of subgastric triradiate, of 

 triradiate spicules of the parenchyma, of subdermal and dermal triradiate spicules. 



Gastric triradiate spicules. — All rays more or less cylindrical ; basal ray straight, thinner than 

 lateral rays, average size 0"325 by O015 mm. ; lateral rays either straight or slightly 

 curved outwards, each forming with basal ray an angle of about 110°; size - 2 to 0\325 

 by 0-02 mm. 



Subgastric triradiate spicules. — Sagittal ; all rays of the same diameter of 0-028 mm. ; basal 

 ray straight, tapering from the base to a sharp point, reaching 0-55 mm. iu length, forming 

 with each of the lateral rays an angle varying from 110° to 120°; lateral rays sharp- 

 pointed, slightly undulating, rarely longer than 0'3 mm., forming with each other an angle 

 varying from 170° to 145°. 



Triradiate spiades of the parenchyma. — All rays of the same diameter, not exceeding 0'0-to 

 mm., usually sharp-pointed ; basal ray straight, forming with each of the lateral rays an 

 angle varying from 115° to 120°, length inconstant, not exceeding 04 mm.; lateral rays 

 either straight or slightly curved, often undulating, attaining a length of - 5 mm., forming 

 with one another an angle varying from 180° to 150" ; not numerous, more or less 

 imitating in their disposition the subgastric triradiate spicules. 



Subdermal triradiate spieides. — In general of the same form as the corresponding spicules in 

 Amphoriscus poculum and Amphoriscus elongatus. All rays of the same diameter (0 - 02-0'025 

 mm.), sharp-pointed ; basal ray straight, rarely longer than - 18 mm., forming with the 

 longer lateral ray an angle of about 110°, with the shorter of about 118°; lateral rays 

 curved outwards, the shorter often undulating, its length not exceeding - 2 mm., the 

 longer curved only at its base, almost straight further on, attaining a length of - 4 mm. 

 These spicules are disposed in such a manner that the angle formed by the basal ray and 

 the shorter of the lateral rays is turned to the outer surface, the longer lateral ray beiug 

 directed centripetally. 



Dermal triradiate spicules. — More or less stout, the proportion between the length and the 

 thickness of the rays varying from 7 : 1 to 12 : 1, some almost regular, all rays being of the 

 same length, not exceeding 0-8 mm., and their angles of 120° ; most either sagittal or 

 irregular, the deviations consisting either in the differentiation of the plane of the ends of 

 the rays and that of their crossing, or in the unequal length of the rays, or iu the sagittal 

 differentiation of the angles formed by basal and lateral rays, these angles varying from 

 120° to 125°, and the corresponding lateral rays growing rather curved outwards. 



Colour. — Dirty yellowish. 



Habitat.— Station 209, January 22, 1875 ; lat. 10° 10' N., long. 123° 55' E.; Philip- 

 pine Islands; depth, 95 to 100 fathoms; mud. 



