254 
They, however, differ from Productus, restricted, in the presence of supplementary 
adductor scars, which are certainly not visible in any of the Australian specimens 
examined by me. Under these circumstances, P. suiqmdratm must for the present 
remain in the older genus, although it would probably simplify the classification of such 
intermediate forms if another genus were established for them, differing from Productus 
as above indicated, and agreeing with Daviesiella in all but the character named. The 
casts of both the dorsal and ventral valves are much pitted towards the front margin, 
and the general surface of the former is covered with jmckmark-like depressions. 
P. suhquadratus is distingui.shed from P. hrachytlioeriis by its much larger size, 
sinus of the ventral valve, length of the septum, much larger area, and lastly the 
dendritic adductor scars of the ventral valve. 
There are some points in common between the present species and Productus 
scabriculus, Martin, such as the bilobate form of the ventral valve, the sinus, and 
generally sjieakmg, the ornamenting spines. Unlike the British species, however, our 
form is remarkably geniculate, is really more deltoid, and not so transverse. Uurther- 
more, the septum is here entire, of great length and development, and the reniform 
impressions much more lateral in position, and placed lower 'down. A single specimen 
oi P . scabriculus has been recorded by De Kouinck from New South Wales, and the 
description leads me to infer that the Author had before him sotne condition of the 
present species. 
Near to P. suhquadratus is Productus Purdoni, an Indian species described by the 
late Dr. Davidson,* both in the form of the shell and general surface characters ; but 
the Indian species is not geniculate, and has a pronounced fold in the dorsal valve. 
Neither of the numerous examples of the former shell examined by me have shown this, 
nor the fine reticulation of the surface described in P. Purdoni by Dr. Waagen.t 
Before concluding, a few words must be said about the siliceous cast figured by 
Morris as Productus brac1iytli(Brus,X and which, although now known not to be that 
species, is at the same time in want of determination. It possesses many points in 
common with P. suhgitadrntus, and in the figure there is a very suspicious indication of 
an area. If the ventral adductor scars could only be shown to be dendritic, the 
resemblance would be complete. I think it not impossible that we are dealing here 
with a small and short form of the present species. 
Loo. and Horizon. Eichards’ Homestead, three miles south-west of Mount 
Britton Township {A. L. Morisset) ; Pelican Creek, two and a-half miles above Sonoma 
Eoad-crossing (P. L. Jach) — Middle or Marine Series of the Bowen Eiver Coal Field 
Lake’s Creek, near Eockhampton {The late James Smith) ; Yatton Gold Field (P. L- 
Jach) — Gympie Beds. 
PBonrcTTTS rNDATUs, Hefrance, PI. 12, fig. 16. 
Productus urdat'US, Defrance, Diet. Soi. Nat., 182G, xliii., p. 354. 
„ „ Davidson, Mon. Brit. Garb. Brach., ISfil, Pt. 4, p. 161, t. 34, f. 7-13. 
„ „ De Koninefe, Foss. Pal. Nouv.-Galle.s du Sud, 1877, Pt. 3, p. 190, 1. 11, f. 4. 
„ ,, Etheridge fit. Cat. Australian Foss., 1878, p. 53. 
Obs. This species is known only by a single specimen, exhibiting the regular 
concenti’ic undulations characteristic of it. The latter are much more uniform and 
continuous than those on the figure of the example from New South Wales given by 
* Quart. .Tourn. Geol. Soc., 1861, xviii., p. 31, t. 2, f. 6a and b. 
t Pal. Indica (Salt Range Fossils , 1884, Ser. xiii., Vol. i., Pt. 4, fasc. 4, p. 706, t. 73, f. 1-3. 
t Strzekeki’s Phys. DesoriiJ. N. S. Wales, &o., t. 14, f. 4a and b. 
