462 REVISION OP THE AXINELLID^.^ i., 



met with, as in T. dlyitatus and T. pusfu/osiis; and the mega- 

 scleres are there of nutablj' greater size than elsewhere. The 

 strongyla are mostly not quite cylindrical in shape, but slightly 

 fusiform; they are of lesser length, on the average, than the 

 oxea, and, in tlie case of the shortest, are I'elatively much stouter. 

 Although sti'ongyla are pi'esent in far greater number than styli, 

 spicules iiitei-mediate in form between them and oxea are of less 

 frequent occurrence than those intermediate between styli and 

 oxea. The maximum size of the megascleres is not greater than 

 480 X 23//. in the bi^anches, and about 530 x 28/^ in the stalk; 

 the oxea are very rarely less than 330/x in length, and propoi'- 

 tionately slender, but the shortest strongyla (which may exceed 

 20/x in stoutness) fall below 200/x. 



MlcrusclpTfix. — The spirulaj are mostly of between 1 and 2 turns 

 and from 2 to 3/x in stoutness; (J-shaped forms are rather scarce, 

 and straight rc^ds rai'e. The microstrongyla are very scarce, 

 seldom centrotylote, and from If) x 3 to 20 x 5/x in size. 



Trachycladus fastigatus, sp.nov. 

 (PL xxi., fig.l; PI. xxiii., fig. 10.) 

 Diagnosis. — Profusely branched. Branches elongated and 

 tapering; anastomosing at points of contact. Surface smooth 

 and glabrous. Oscula (?). Dermal layer strongly developed, 

 dense, opaque; with ck)sely packed spirulie forming a layer 70- 

 140/i. tliick. Inhalant pores dispersed singly. Skeleton with a 

 rather dense axial fune, of diameter generally less than the length 

 of the radial fibres. Radial fibres directed at an angle of from 

 35° to 60° with the skeleton-axis; very rarely more than 20-25/a 

 in stoutness; their spicules cemented by a scarcely perceptible 

 amount of spongin. Extra-axial connecting fibres few, mostly 

 unispicular. Megascleres almost exclusively diactinal, mostly 

 more or less rounded ofi' at the ends, very commonly approximat- 

 ing in form to strongyla, but nearly always more or less (slightly) 

 fusiform; only slighter, if at all, of greater dimensions in the 

 stalk than elsewhere; in maximum size very rarely exceeding 

 520 x 9/u, and at most 560 x 12/u. Microstrongyla abundant in 

 some parts, scarce in others. 



