BY R. VON LENDENFELD, PH.D. 507 



surface. In such cases the lacunose tissue formed by the congre- 

 gatiou of the exhalent canals extends also down to the vestibule 

 space. 



No oscula are found either in the skeletons part or in the walls 

 of the vestibule cavity. 



Skeleton. 

 (Plate 36, fig. 1.) 



The main fibres of the skeleton radiate from the point of 

 attachment outward and upward. They extend mainly in a 

 longitudinal direction and branch in a more or less penicillate 

 manner. The main fibres are joined on the surface to the sand- 

 armour, and it is clearly visible that their sand-core is a direct 

 continuation of the sand in the skin. 



The main fibres curve gracefully outward in their distal portions 

 and all their ends are joined to the outer skin. Never is a free 

 termination of a main fibre formed in the interioi\ This shows 

 that these main fibres grow in the same manner, as the main fibres 

 of Halme, namely just below the outer skin. 



It is also very remarkable that no main fibres are joined to the 

 inner skin on the vestibule side of the lamella. 



The consequence of this is that the skin can be drawn off on 

 the inner side, whereas it appears firmly attached on the outer. 



In detail the main fibres, although always completely filled 

 with foreign bodies differ in the different vai'ieties, and these 

 details shall be described below. 



The connecting fibres form, as mentioned above in the diagnosis 

 of the sub-genus, two systems. Thicker primary tangental, and 

 thinner secundary radial connecting fibres are distinguishable. The 

 mode of ramification varies in the varieties, and shall be 

 described below. The connecting fibres never contain foreign 

 bodies. 



It is most remarkable that round the grooves in the skeleton 

 filled by the lacunose, askeletous tissue, the connecting fibres 

 terminate with sharp points. (Plate 37, fig. 1, b.) This is 



