KEPORT ON THE HEXACTINELLIDA. 123 



gradually narrowed inferior portion into the obliquely inserted, round, hollow stalk, 

 which is 3 mm. in diameter, and has been torn off at a distance of 3 cm. from the body. 

 The upper transversely truncated extremity of the latter exhibits the circular aperture 

 (9 mm. in width) of a simple gastral cavity, which is 2 mm. in depth, and ends beneath 

 in a blind sack-like manner. The tolerably compact body-wall is about 5 mm. in thick- 

 ness beneath, and becomes gradually attenuated upwards to the narrow smooth border 

 of the opening. I was not able to observe a direct continuation of the gastral cavity 

 into the cavity of the tubular stalk, though such a connection may be present. 



Among the principalia of the parenchymal skeleton the strong regular hexacts with 

 simple smooth rays occupy the first place. Diacts of variable length, however, with 

 pointed or rounded extremities, occur scattered or in bundles and disposed in different 

 directions. They are for the most part destitute of any central swelling, but the 

 intersection of the axial canals is frequently recognisable. 



Between these large parenchjrmal spicules numerous small regular hexacts occur, with 

 strong rays which decrease in diameter towards the extremities, which are beset with 

 small thorns and bear at the very tip a small arched terminal disc with six or more 

 bent marginal ^jrongs. Sometimes, too, one or other ray may be found to be divided 

 almost to the middle into two or three diverging branches. These exceptional forms 

 lead to a rosette which occurs here and there, and is figured in PI. XXIII. fig. 12. 

 Here four to six strong diverging terminals, half the length of the principals, stand on 

 each extremity of the proportionally long, smooth or slightly tuberculated, principal rays. 

 These straight or slightly bent thin terminal rays are provided with lateral thorns, and 

 bear on each of their extremities a transverse disc provided with several marginal prongs. 

 Another rosette which is figured in the same plate (figs. 10, 11) occurs far more abundantly 

 than the form mentioned. This consists of long smooth principal rays which are 

 terminated by a small discoid expansion. The flat outer surface of the disc bears a 

 tuft of short delicate terminal rays provided with pronged terminal discs. The outermost 

 circle of terminals, are bent in an S-like manner. 



The essential agreement between the dermal and gastral skeleton is here particularly 

 manifest. The transition from the one to the other occurs quite imperceptibly on the 

 rounded margin of the large oscular opening (PL XXIII. fig. 14). 



Both hypodermalia and hypogastralia are strong and tolerably large pentacts, in 

 which each of the strong radial principals is beset on its middle portion with isolated 

 spines, while the four transverse rays are smooth throughout. 



The autodermalia are hexact pinuli with broad, scaly, pronged, oval, fir-cone-like distal 

 rays, while their moderately long proximals, like the somewhat longer transverse rays, 

 remain quite smooth (PI. XXIII. fig. 13) up to the conically narrowed, rough or pronged, 

 terminal portion. The autogastralia difi'er from the autodermalia only in their smaller 

 breadth, and in the more slender, smooth basal portion of the freely projecting scaly ray. 



