66 
can be little doubt that A. reticularis is a very characteristic shell of the Panning 
Limestone. The larger number of the specimens arc a good deal weathered, but in the 
original example “ the characteristic decussating frills or laminfe are preserved on both 
valves, but they are seen to much greater advantage on the ventral valve.” One of the 
recently collected specimens, apparently of this species, shows traces of the spines 
around the broken edges of the shell. 
The only apparent real difference between this species and the next, is the 
presence of the area in the latter. This however, varies much, both in length and 
height, and at times is even very difficult to distinguish. Indeed, from an examination 
of these specimens I can quite understand the late Dr. Davidson’s difficulty, expressed 
in the following words — “ I am very uncertain whether Atrypa desguamata be really 
more than a variety of A. reticularis." 
Hoc. Panning Diver, Burdekin Downs, and Panning Old Station. (i2. L. Jaclc.') 
Atetpa desquamata, J. de G. Bowerhy, PL 4, figs. 2, 3; PI. 37, fig. 8. 
Atrypa dcsqxiamata, 3. de 0. Sby., Trans. Geol. Soc., 1840, 2d. Ser., v., Expl. of t. 56, t. 56, f. 19, 20. 
,, ,, Davidson, Mon. Brit. Dev. Erach., 1804, Ft. 1, p. 58, t. 10, f. 9-13, t. 11, f. 1-9 (for 
synemymy). 
„ ,, Etheridge fil., Proe. R. Phys. Soc. Bdinb., 1880, v., p. 270, t. 7, f. 3, 4. 
Ol}s. Prom the series of figures of Atrypa desguamata given by Dr. Davidson, 
it is quite clear that the species is one of considerable variation, both in the relative 
dimensions of the shell, from the hinge lino or beak to the front margin, and also 
laterally, from side to side, the result being that the length of the hinge line is also 
variable, short in some varieties, longer in others. 
We possess several shells from the Panning Diver Beds which are more 
than probably this species. If we take the best preserved of these, we find that 
it is very much more transverse than those represented by Dr. Davidson on PI. x. 
of his Devonian Monograph, but not more so than some of the figures of PI. xi. 
of the same work. Again, the relative convexity of the valves when in apposition 
is very much less than Dr. Davidson’s fig. 15 of PL xi., but is a little more pronounced 
than the fig. 3® of the same plate. Even among the three Queensland examples 
the shape varies somewhat. The ribbing of the valves corresponds with that seen 
in A. desgtiamata, and there are also traces of concentric laminfe. The above Author 
laid stress on the exposure of the foraminal aperture and presence of an area. Both 
are to a certain extent visible in one of the earlier specimens collected. In one of 
the more recently acquired examples the beak of the ventral valve is very acute and 
prominent. The strength of the surface eoste or ribs is not in every case equal, 
some being much more prominent and pronounced than others. The ventral valves 
are gently but regularly curved, and there is a moderately pronounced sinuatiou in the 
front margin. 
Professor McCoy appears to have been the first to describe* the spiral 
appendages in A. desguamata, and they have since been figured in their entirety 
by Dr. Davidson. t It is interesting to note that two of the specimens under 
description exhibit traces of these appendages from the shell having been removed by 
weathering. 
Loc. and Horizon. -Limestone of the Panning Diver, and shale above the Fanning 
Limestone, at Panning Old Station, Burdekin Dowms. (72. L. Jaclc.) 
Brit. Pal. Foss., 1852, Fas. 2, p. 379. 
t Loc. cit., t. 11, f. 7, 8. 
