CALCAREA. 23 



(d) Alate triradiates from the dermal cortex. Basal ray nearly straight, bluntly 

 pointed, 80 fi to 140 m long x fx to 10 m thick. Paired rays unequal, 

 slightly curved upwards, often longer than the basal ray, 65/t to 150 m 

 long X 8 M to 10 /u thick. Oral angle 100° to 110°. 



The Quadriradiates are of one sort : — 



('') Alate quadriradiates from the gastral layer. Basal ray straight, tapering 

 uniformly to a sharp point, 500 m to 700 m long x 10 m thick. Paired rays 

 usually equal, slightly bent in either direction, 100m to 230m long x 8m 

 to 11m thick. Oral angle 130°. Apical ray nearly straight, sharply 

 pointed, 70 m to 100m long x Gm thick. 



Oscular spicules. — The fringe is formed of oxea of types (a) and (A). 

 The oscular edge is formed of small quadriradiates similar to (f), but smaller. 

 Basal ray 100 m long x 8 /x thick. Paired rays about 100 /x long. 



Dermatreton hodgsoni.* 

 • (Plate XXVII., Fig. l, and Plate XXXII., Figs. G5-74). 



There is only one specimen of this new species in the collection. It is bent and 

 irregularly swollen (see Fig. 1), the length being 60 mm. and the maximum diameter 

 14 mm., tapering at both ends to about 3 mm. It is quite white as preserved in 

 alcohol. To the naked eye the surface appears to Ije smooth and minutely reticulated 

 The walls are delicate, only 1 mm. thick at their thickest point. 



The structure of the body wall is partly shown in Fig. 73. The flagellated 

 chambers open through contractile apopyles into excurrent chaml)ers, three or fom- into 

 each, and these in turn ccnnmunicate with the gastral cavity through large irregular 

 ports. The excurrent chambers have no proper skeleton, but are merely spaces left 

 between the proximal ends of the chamliers and the gastral layer. Four of the 

 flagellated chambers opening into an excurrent chamber are shown in Fig. GG. 

 The .skeletons are drawn and the interior linings indicated by dotted lines. A cross 

 section of the same excurrent chamber is shown diagrammatically in Fig. 67. The 

 form of the excurrent chambers varies widely, they are often much deeper than the 

 one illustrated. The flagellated chambers have ordinary articulated skeletons of many 

 joints, strengthened at the distal ends by oxea, which project a short distance beyond 

 the dermis, and also l)y long hair oxea, which project with the thicker oxea and extend 

 inwards nearly to the gastral layer. The " linked " arrangement of the flagellated 

 chamljers is shown in Figs. 68, 69 and 70. Fig. 68 shows the ports in the gastral layer, 

 Fig. 69 the flagellated chaml)ers just above the gastral layer, and Fig. 70 the same 

 chambers higher up, arranged in a "linked" pattern. All three figures are drawn 



* The author ventures to n.ame this species after Mr. T. V. Hodgson, the biologist of the Expedition, to 

 whose untiring industry and ingenuity the magnitude of the collection is due. 



VOL. IV. 2 L 



