TLACOSOMA PAKADlCTYUM. Ö 



some parts of the margin, the lattice simply becomes gradually 

 unrecognizable as such, without a distinct demarkation to delhnit 

 it ; but the more usual condition is that there exists a rather 

 sharply defined boundary. This consists either in a low and 

 narrow wall-like ridge which is more or less distinctly inclined 

 towards the front, or in that the angular body-edge is gently 

 curved forwards, the concave surface being lined by the lattice 

 up to the very edge and the convex, by the dense-looking cover- 

 ing of the back, presently to be described. The latter condition 

 reminds one strongly of that of the oscular margin in many 

 cup-like Hexactinellids with the outflaring rim. 



On the iMck of the body the surface is much wrinkled or 

 puckered up (PL I., fig. 2). Here, as on the entire stalk, a 

 lattice-like arrangement of dermal spicules is not perceptiljle ; the 

 subdermal space is scarcely developed, or at any rate is (juite 

 insignificant. The entrances into incurrent canals are, if at all 

 developed, small and indistinct. The dermalia are intimately 

 associated with spicular elements of other categories and serve, 

 together with these, to give to the surface a closely interwoven, 

 opaque appearance. The superficial tissue thus formed is soft 

 and extremely delicate, resembling a pith both in appearance and 

 texture. — Further, this side of the body is, as before indicated, 

 peculiar on account of the presence of oscula. These occur even 

 on the stalk, but are confined to the same side. I distinguish a 

 large primary or main osculum and numerous much smaller 

 oscula of probably secondary origin. 



That which I consider the primanj osculum, is a roundish 

 opening situated on the upi)er, broad and irregularly rounded 

 edge of the body, Avell without the border of the frontal lattice. 



