DENDY—REPORT ON THE CALCAREOUS SPONGES 17 
Leucaltis bathybia var. mascarenica Ridley [1884]. 
FHeteropegma nodus gordu von Lendenfeld [1885]. 
Clathrina latitubulata Carter [1886 ]. 
Heteropegma nodus gordi Dendy [1892]. 
Heteropegma latitubulata Dendy [1892]. 
Heteropegma nodus-gordit Dendy [1893]. 
Heteropegma nodus-gordw Hanitsch [1895 |. 
Heteropegma nodus Gordw Bidder [1898]. 
Heteropegma nodus-gordi Dendy [1905]. 
Heteropegma nodus gordi Jenkin [1908]. 
This widely distributed species is well represented in the collection by a number of 
fine specimens. It is easily recognizable by its external form, consisting of an irregular 
mass of anastomosing tubes resembling a reticulate Lewcosolenia, on an enlarged scale. 
This form has been well illustrated by Poléjaeff in the “Challenger” Report, and I need 
only add that the diameter of the tubes varies considerably in different specimens and 
is often much greater than represented in Poléjaeft’s figures. 
It is unnecessary to figure the typical external form again, but I give photographs of 
two specimens to show the range of variation in this respect (Plate 2, figs. 1, 2). 
The wall of the tube always consists of three sharply defined layers, each with its 
own characteristic spiculation. On the outside we have the well-developed dermal cortex, 
supported by tangentially disposed triradiates and quadriradiates, of large but variable 
size. The quadriradiates are commonly larger than the triradiates and the apical ray 
projects inwards towards the gastral cavity, but the extent to which quadriradiates are 
developed varies very greatly in different specimens and they may be very scarce. 
The middle layer consists of the branching, radially arranged tubes, lined by collared 
cells, whose walls are supported only by the very small, regular triradiates and quadri- 
radiates, with very slender rays, and to some extent by the apical rays of the large 
dermal quadriradiates. 
The inner layer is a thin gastral membrane, extending between the exhalant openings 
of the radial tubes and supported by a single layer of minute sagittal triradiates and 
quadriradiates. The ends of the facial rays are often swollen, but to a very variable 
extent, and the apical rays of the quadriradiates are often very long and thick in 
proportion to the slender facial rays. 
The general anatomy has already been figured by Poléjaeff and myself, and the 
spicules have been figured more or less satisfactorily by Haeckel, Poléjaeff and Jenkin. 
I am able to confirm Bidder’s statement as to the basal position of the nuclei of the 
collared cells. 
A careful examination of Haeckel’s type-specimen of Leucaltis clathria, fragments 
of which were brought from Jena by my colleague, Mr R. W. H. Row, leaves no doubt 
that it is a “ Heteropegma” and specifically indistinguishable from the species obtained 
by the “Challenger” and named by Poléjaeff ““ Heteropegma nodus gordu.” Haeckel’s 
figures of the large spicules are good. His fig. 3¢ is evidently a portion of the gastral 
membrane with the characteristic minute sagittal tri- and quadriradiates. The shape of 
SECOND SERTES—ZOOLOGY, VOL. XVI. 3 

