BY K. F. HALr.MANX 531 



The megascleres forming the radial fibres are notably longer, 

 on the average, than those of the axial skeleton; while the 

 longest spicules of all ai"e found in the surface-tufts. Sigmata 

 are present in great number, and occur for the most part 

 arranged uniserially along lines which probably coincide with 

 the courses of the main canals; they are of two sizes, the larger 

 being much the more numerous. Short, slender microxea (un- 

 mentioned in the original description) are also present, but 

 appear to be rare; apparently also, they occur only singly 

 scattered, never in dragmata. 



Spicides. —(i.) The megascleres are almost exclusively styli, 

 usually of slightly lesser diameter at the base than at some dis- 

 tance therefrom, and tapering towards the apex; frequently 

 more or less blunt-pointed apically, and occasionally passing into 

 strongyla, those of the latter form being almost invariably of 

 less than the average length; often abruptly somewhat blunt- 

 pointed at the basal end, but very rarely becoming oxea; ranging 

 in length from about 300 to 640/x, and in stoutness from rarely 

 less than 10 to about 26/1. The shorter spicules are generally 

 straight or nearly so, the longer are nearly always slightly 

 curved, or sometimes bent, the flexure as a rule being mainly in 

 the basal moiety of the spicule. 



(ii.)The two kinds of sigmata are scarcely different except 

 with respect to size. The smaller vary in length from 12 to 

 (rarely) 20/x, the larger from 25 to 40/u, measured from bend to 

 bend; the maximal stoutness is in each case about 2)u.. Thev 

 are, without exception, more or less contort,— often (especially 

 in the case of the larger ones) to such an extent as to appear 

 3-shaped. 



(iii.) The microxea (trichites) are fusiform, 25 to 35/x in length, 

 and at most l'5ju, in diameter. 



SiGMAXINELLA VIMINALIS, Sp.nOV. 



(PI. xxxiii., fig. 4; PI. xxxv., figs.l, 2; PI. xxxvi., fig.l.) 

 Diagnosis. — Ramose, erect, stipitate; with elongated, slender, 

 cylindrical, tapered branches, disposed irregularly. Surface 

 hispid. Oscula, if present, small and inconspicuous. Dermal 



