EEPORT ON THE HEXACTINELLIDA. 175 



with the thickness of the wall, and thus differs very greatly in the different regions of 

 the body. The subdermal trabecular framework, extending between the dermal membrane 

 and the chamber layer, exhibits only here and there irregular gaps, while the similar 

 subgastral framework following the concave curvature of the chamber layer exhibits 

 wide lacunae, which extend into the gastral membrane. A thin layer of the trabecular 

 framework also extends on the inner surface of each concave diverticulum (PI. LX. fig. 3). 

 The connected lattice framework of the skeleton consists of medium-sized hexacts, 

 which are united in an irregular fashion either by fusion or by synapticula (PI. LX. 



fig-3). 



As can be readily seen in the older portions of the framework, with the help of the 

 much enlarged axial canals, the six rays stand, as a rule, at right angles to one 

 another, but frequently bend from their original direction, and become, as they approach 

 the rays of other hexacts, united with the latter by lateral mooring or by synapticula. 



From the complete absence of a regular orientation and mode of connection, it seems 

 to me preferable to refer Aulocalyx not to the Dictyonina but to the Lyssacina. In the 

 closer regions of the skeletal framework, between the medium-sized hexacts, numerous 

 small forms occur with short, thick rays, rounded off at the ends, and with a much expanded 

 central portion. These are irregularly scattered, and are united with the former, so that 

 a very close, spongy skeletal meshwork often results. 



As to the isolated spicules which occur between the beams of the skeletal framework, 

 either scattered quite irregularly in the parenchyma, or limited to certain regions of 

 the same, I ought first to mention the fine, small, regular oxyhexacts, which occur 

 irregularly, but in considerable abundance, through the whole parenchyma (PL LX. fig. 3). 

 They always exhibit a slight roughening of all their rays. Besides these, numerous 

 in*egularly distributed, small, regular discohexasters occur, in which, from each of the 

 moderately large, simple, smooth main rays, a tuft of S-shaped thin terminals project in 

 perianth-like arrangement. Each of the terminal rays exhibits a somewhat thickened 

 end, bearing a convex terminal disc with marginal teeth (PI. LX. figs. 4, 6). 



The length of the main rays and the number of terminals on each are the same in 

 one and the same discohexaster, but vary in the different rosettes, of which two very 

 different specimens are figured in PI. LX. figs. 4, 6. 



Another quite unique and characteristic form of rosette occurs, only however in the 

 •subdermal trabecular space, but there in comparative abundance. It is distinguished 

 by its conspicuous size and by its peculiar structure, as represented in PI. LX. figs. 3, 5. 



These perfectly regular rosettes have a diameter of 0'4 mm. From each of the 

 relatively short, smooth main rays, six terminals arise, arranged in a whorl, and disposed 

 at equal angles in a funnel-like manner. These long terminals are either straight or some- 

 what convexly curved at their narrow base, and gradually increase in thickness in club-like 

 fashion toward the simply convex, or more rarely somewhat knobbed external end. They 



