804 DR. G. J. HINDE ON RECEPTACULITIDA, 
cylindrische Rohre, Dames ; Saiulchen, Giimbel; cells, Hall, Meek, 
and other American paleontologists ; trous ronds, Defrance), the 
name “ vertical ray’ may be used. As regards the relative position 
in the organism of the spicular plates and rays, that angle of the 
summit-plate and the horizontal ray beneath it which point towards 
the basal nucleus or commencement of growth of the organism (one 
of the radial stolons, Bill.; radial-centripetaler Ast, Gumb.) may be 
termed the “ proximal angle and ray ;” whilst the angle and ray 
pointing in the opposite direction, that is, towards the periphery of 
the organism in the flattened examples, or towards the summit in the 
conical forms (radial-centrifugaler Ast, Giimb.), will be the “ distal 
angle and ray.” The other two angles of the summit-plate and the 
corresponding rays (= cyclical stolons, Bill. ; concentrische Aestchen, 
Gimb.) may be named “ lateral angles and rays.” Thus in those spe- 
cimens in which the head-plates of the spicules have been removed, ° 
and the surface below them appears as if divided into small rectal- 
gular spaces, the lines radiating from the nucleus to the periphery, 
or to the summit in conical examples, are formed by the distal and 
proximal rays of the spicules, whilst the lines crossing the former at 
right angles, and preducing concentric circles, are formed by the 
lateral rays. 
For the inner or upper integument in the genus Receptaculites 
(=Endorhin, Bill.; innere Hulle, Gumb.) I propose merely to use 
the term “inner layer.” 
IL. MryneRAL STRUCTURE AND ASPECT UNDER DIFFERENT 
ConpDITIONS OF PRESERVATION. 
One of the first considerations in relation to the true nature of 
these fossils, and one to which little attention appears to have been 
directed by those who have hitherto studied them, is that of their 
original mineral constitution. The generally accepted conclusion of 
the Foraminiferal nature of Leceptaculites appears to have lulled any 
suspicion that might have been entertaimed as to the originally 
calcareous constitution of its skeleton; and even in the solitary 
instance in which a serious attempt has been made by Mr. Billings 
to compare its structure with that of spicules of siliceous sponges, 
there is no evidence brought forward to show the probability that 
its skeleton may have been also originally siliceous. ‘Though, in the 
majority of examples, the skeleton is now of carbonate of lime, yet, 
so far as I am aware, not a single specimen has been found in which 
this mineral is otherwise than in a crystalline condition, and cannot 
therefore be regarded as the original structure of the organism. 
This circumstance alone is sufficient to show that there is a prima 
facie ground for questioning whether some other mineral than calcite 
may have formed the hard parts of the organism. The extraordinary 
diversity of appearance which Aeceptaculites and its allies exhibit, 
according to the different conditions in which the skeleton is pre- 
served, stands also in intimate connexion with the question of its 
original nature, and renders it of importance to ascertain this point 
by a comparison of the different condition of these fossils from strata 
