124 ROYAL SOCIETY OF CANADA 
specimens collected by Mr. Richardson are much more like the Thetis 
circularis, as figured by Meek and by Whitfield, than they are to Gabb’s 
illustrations of C. dubius. 
CLisocoLus CORDATUS, Whiteaves. 
Clisocolus cordatus, Whiteaves. 1879. Geol. Surv. Canada, Mesoz. Foss., vol. i., 
p. 157, pl. 18, figs. 3, 3 a-b, but probably not Cyprina cor- 
data of Meek and Hayden (1857) nor Clisocolus dubius, 
Gabb. 
ss F White. 1889. Bull. U. S. Geol. Surv., no. 51, p. 41, pl. 6, figs. 
8 and 9. 
The identification of the Sucia Islands specimens collected by Mr. 
Richardson with the species from the Fox Hills group of Dakota, which 
was first described by Meek and Hayden as Cyprina cordata and subse- 
quently by Meek as Sphæriola cordata, has not proved satisfactory, and 
they seem to be quite distinct from Gabb’s Clisocolus dubius. 
CYTHEREA NITIDA, Gabb. (Sp.) 
Cytherea Leonensis, Etheridge. 1861. Quart. Journ. Geol. Soc. Lond., vol. xvii., 
p. 482, but not C. Leonensis, Conrad, 1857. 
Cytherea Conensis (err. typ. for Leonensis), Etheridge. 1863. The No. 42 of the list 
of specimens on page 248 of Capt. Palliser’s official report. 
Venus (Mercenaria ?) varians, Gabb. 1864. Geol. Surv. Calif., Palæont., vol. i., p. 
161, pl. 23, figs. 140 and 141. 
Meretrix nitida,Gabb. 1864. Jb., p. 165, pl. 23, figs. 145 and 146. 
Chione varians, Gabb. 1869. Geol. Surv. Calif., Palæont., vol. ii., p. 239. 
Caryatis nitida, Gabb. 1869. Zb., p. 240. 
Cytherea (Caryatis) plana, Whiteaves. 1879, Geol, Surv. Canada, Mes 
vol. i., pt. 2, pl. 17, figs. 14, 14 a-b; but probably not 
“Venus planus,” Sby., nor Aphrodina Tippana, 
Conrad. 
The writer has long been convinced that the specimens from Hornby, 
Vancouver and the Sucia islands, which he identified with the ‘“ Venus 
planus” of Sowerby, in 1879, are not that species, but the Caryatis mtida 
of Gabb. In December, 1892, Mr. Stanton examined these specimens 
while on a visit to Ottawa, and expressed the opinion that they could not 
be distinguished from Chione varians, Gabb. Since then Mr. Stanton has 
forwarded a series of each of these nominal species from the Chico group 
of California, and both he and the writer have quite independently come 
to the conclusion that the characters which Mr. Gabb relied upon to dis- 
tinguish his Caryatis nitida from Chione varians are neither constant nor 
sufficient to justify their separation. 
