1584 THE VOYAGE OF H.M.S. CHALLENGER. 



In some specimens of this species all the tubes bear two or three terminal branches, whilst in 

 others there are tubes with four, five, or six branches intermingled. When the number of the 

 terminal branches is constant in single localities, this transformistic or " Darwinian " species may 

 be divided into the following "subspecies:" (1) Auloceros pandora (with variable numbers); (2) 

 Auloceros bifurca (fig. 2) ; (3) Auloceros trifurca (fig. 3) ; (4) Auloceros quadrifurca (fig. 4) ; (5) 

 Auloceros quinquefurca (fig. 5) ; (6) Auloceros sexfurca (fig. 6). 



Dimensions. Length of the tubes To to 2'5, breadth 0'02 to 0'03 ; branches O'Oo to 015 long. 



Habitat. North Pacific, Stations 231 to 253, surface and at various depths. 



2. Auloceros trigemimts, n. sp. (PI. 102, fig. 7). 



Eadial tubes club-shaped, gradually thickened towards the inflated distal end. Terminal 

 branches short, scarcely longer than the tube is broad, two constantly opposite, each with three 

 equal, conical, short secondary branches. No terminal spathillae. 



Dimensions. Length of the tubes O6 to 0'8, breadth 0'02 to 0'03 ; branches 0'04 to 0'08. 



Habitat. North Atlantic, Station 353, depth 2965 fathoms. 



3. Auloceros capreolus, n. sp. (PI. 102, fig. 8). 



Eadial tubes cylindrical, equally broad. Terminal branches in two opposite clustered bunches, 

 each with sixteen to eighteen unequal secondary branches. The total length and breadth of each 

 cluster is about four times as great as the tube is broad. No terminal spathillas. 



Dimensions. Length of the tube 1'5 to 2'0, breadth 0'03 ; branches 0'07 to O'l. 



Habitat. South Pacific, Station 295, depth 1500 fathoms. 



4. Auloceros cervinus, n. sp. (PI. 102, figs. 9, 10). 



Eadial tubes slender, spindle-shaped, slightly curved, tapering gradually from the middle 

 towards the two ends. Terminal branches constantly three, obliquely ascending, each twice or three 

 times forked (often more or less irregularly), with slender, curved, secondary and tertiary branches 

 (twenty to twenty-four on each tube) ; the latter are scarcely half as broad as the three main 

 branches of each tube. No terminal spathillae. 



Dimensions. Length of the tubes 2 - to 3'5, breadth 0'03 to 0'04; branches 012 to 015 long. 



Habitat. South Atlantic, Station 325, depth 2650 fathoms. 



5. Auloceros elegans, n. sp. (PL 102, fig. 1). 



Eadial tubes slender, cylindrical, straight, equally broad. Terminal branches two or three, 

 more or less irregularly branched, each with twelve to eighteen curved and pointed secondary 

 branches. No terminal spathillae. Differs from the preceding Auloceros cervinus in the cylindrical 

 form of the thinner straight tubes, and the more irregular ramification ; the branches are nearly 



