20 
K. L. PREXDERGAST. 
LINOPRODUCTUS Chao. 
1927. — Chao, Falaeoni. sinica, ser. B, V, fasc. 2, p. 128. 
1928. — Chao, ibid, fasc. 3., p. 63. 
1931. — Paeckehuann, pp. 75, 206. 
Genotype. — Productus cora d'Orbigny, 1842, Vov. Amer, Merid., vol. 3, Pal., 
p. 55, pi. V, figs. 8-10. 
Diagnosis. — Thin-shelled Productids with convex pedicle valve; brachial 
valve flat or concave in visceral portion, sometimes geniculated anteriorly. 
Hinge-line equal to or less than the greatest width. Both valves without 
-cardinal area. Pedicle valve evenly convex or sinuate. 
Surface ornamentation of fine radiating striae and indistinct concentric 
wrinkles; wrinkles more marked on the brachial valve. Scattered spines on 
striae present or absent. 
Pedicle valve with marginal ridges weak and muscles not strongly 
impressed. Median septum in brachial valve. No brachial cones. 
Bemarlx'S. — Chao has divided Linoproductids with wavy undulations and 
pustulose spines into two groups, one characterised by P- cancriniformis 
(Tschernyschew), and the other by P. villiersi d^Orbigny. These groups are 
separated by the character of the brachial valve, regularly concave in 
P. villiersi and geniculate in P. cancriniformis. 
Linoproductus cora (d’Orbigny). 
1842. — Product'us corn d’Orbiguy, p. 55, pi. v, figs. 8, 10. 
1911. — Producius cora d ’Orbigny, Diener, p. 19, pi. iii, figs. 3-13. 
1914.“ProdHcf«.S‘ cora d ’Orbigny, Kozlowski, p. 48, pi. iv, fig. 19 ; pi. v, 
fig. 5; pi. vi, figs. 1-10; text-fig. 8. 
1916. — Productus cora d’Orbigny, Broili, p. 19, pi. cxv (1), figs. 14-15; 
pi. cxvi (2), figs. 1-3. 
1927. — Productus cora d’Orbiguy, Chao, p. 132, pi. xiii, figs. 17-18; pi. xiv, 
figs. 1-4. 
1927. — Productus cora d’Orbigny, Diener, p. 24. 
For complete synonymy see Broili (1916) and Diener (1911). 
Diagnosis. — Linoproductids of variable size, transversely oval to elon- 
gated oval in shape, hinge-line equal to gi'catest width of shell. 
Pedicle valve swollen, evenly convex in longitudinal profile, medially 
rounded or with broad sinus ; tendency to spread and flatten in fan-like form 
anteriorly; flanks sloping steeply from visceral portion. Shell arched over 
hinge-line, umbo incurved, slightly overhanging the hinge-line. Ears flat, 
their surface perpendicular to flanks of valve. Ornamentation of fine raised 
and rounded striae, subparallel or flexuous and irreg^ular; increasing in num- 
ber by intercalation of new striae between those pre-existing. Concentric 
folds on ears, not crossing visceral disc. Row of spines along hinge margin, 
spines present or absent on rest of valve. 
Description. — Productus cora was first described by d’Orbigny from 
South America, but the incompleteness of his description led to confusion in 
the interpretation of the si^ecies for many years. The examination of a 
large number of topotypes by Ivozlowski in 1914 showed that there was a 
large variation Avithin the species, and his description is here summarised. It 
varied in shape from transversely to longitudinally oval; the pedicle valve 
might be very SAVollcn in the median region or only moderately so ; the umbo 
was sometimes, but hot always, strongly incurved; the pedicle valve Avas 
