226 MR, J. T. CUNNINGHAM ON 



markings were not to be explained by any effect of crystallization, 

 but were clue, as in the case of molluscan shells, to the successive 

 addition of accretions in a particular direction. The resemblance 

 to molluscan shells consisted in (a) external form, (b) markings. 

 In form the plates of paraffin resembled in some cases Lamelli- 

 branch shells, varying as these do in the proportion of breadth to 

 length, and the narrower ones were more like Brachiopod shells. 

 In all cases there was a prominence corresponding to the umbo 

 of a shell. One specimen had a spiral twist like that of a 

 Gastropod, only flatter; Kappers compares it with the spiral 

 operculum of Txirbo. With regard to markings, all the specimens 

 showed parallel or rather concentric lines or stria?, having in the 

 Lamellibranch-like forms the umbo for a common focus, in the 

 spiral forms being parallel to the edge. These lines are closely 

 similar to the lines of growth in molluscan shells, except that they 

 are slighter, not forming such projecting ridges as in true shells, 

 and never as in the latter furnished with spines or processes. 

 One important difference between the paraffin simulacra and real 

 shells, was that while one surface in the former was convex and 

 bore the concentric markings, the other was in all cases flat, 

 though not smooth, in fact was precisely similar to the free 

 surface always formed when a mass of molten paraffin-wax is 

 cooled in a vessel or a mould. In a shell the inner surface is 

 always concave and smooth. 



It seemed to me that the paraffin plates or simulacra of shells 

 consisted of successive layers superimposed one on another, each 

 succeeding one being larger in area than the one below, and the 

 lines on the convex surface being the edges of the successive 

 layers. If this were the case, there would be a real, though not 

 an exact, resemblance between the paraffin masses and molluscan 

 shells, for it is well known that in the growth of the latter 

 additions are made both to the edge and to the inner surface ; 

 the mantle secretes over its whole surface, and as it grows each 

 successive layer is larger than the preceding and extends beyond 

 its edge. 



Something was said by Mr. Burne about the paraffin simulacra 

 having been formed by cooling with water, and I therefore made 

 experiments by pouring molten paraffin-wax into water. The 

 success was immediate : the wax is lighter than water and 

 therefore floats, and when the cooled mass was taken out it was 

 in all respects similar to the specimens obtained by Kappers. 

 The exact shape of the mass depended on the way in which the 

 molten mass was poured into the water. If it was poured down 

 the side of the basin the mass remained attached to the latter,, 

 and the flow extended away from it : then the shape resembled 

 that of a Brachiopod shell. When the wax was poured on to the 

 free surface of the water, it spread out more evenly and took the 

 form of a cockle or pecten. The first wax to touch the water 

 forms the umbo, that which follows flows over it and spreads out 

 in ever widening layers. The stream of wax must always be 



