36 
i)r. Hind further says no one has recognised the presence of Entolium 
in Cretaceous rocks, Mr. C. B. Boyle’s Catalogue and Bihliography of 
North American Mesozoic Invertehrata^ records on j). 119, as follows: — 
“ Entolium n. snh-gen. iVleek. (1865).” 
By again referring to p. 37, under Amussium, of Avhich Aleek 
constituted Entolium a suhgenus, the American Mesozoic type referred to 
thus ; — 
“Amussium auraimum n.s. Meek. (1865). 
Formation: Jurassic [Cretaceous ?].” 
Mr. E. Philippi also refers several times to the existence of Cretaceous 
Entolinms. 
Entolium aviculatum. Swallow, sp. (?). 
(Plate XV, Figs. 1-L) 
Entolium aviculatum (Swallow), Meek, Hayden’s Final Rojiort U. S. Geol. Survey Nebraska, 
Pt. 2, 1872, p. 189, t. 9, f. 11 a-f. 
Entolium, sp, Eth, fib, Rec. Geol. Survey N. S. Wales, 1891, IV, Pt. 1, p. 35, t. 7, f. 15. 
Observations . — Our specimens exhibit the following characters : — 
Shell suhorhicular, lenticular, compressed, suhequivalvc ; cardinal margins 
very short, straight in the right valve, concave or emarginate in the left ; 
nnilios small, acute, and from them in a downward direction the anterior and 
posterior lateral margins are straight, or a trifle concave for slightly loss than 
one-third the length of the valves, then they hecome Mxdl rounded, and in 
conjunction with the ventral margins form nearly a semicircle ; auricles 
small, in the left valve connate-rectangular, elevated, in the right rectangular 
simply, hut in l)oth valves externally separated from the general surface hy 
impressed lines. From the umbo in each valve diverge two faint linear 
impressions, reaching nearly to the anterior and posterior lateral margins. 
Sculpture of remarkably close, delicate, concentric lines, with traces of 
equally fine radii ; V-sculpture not observed. 
* Boyle — Bull. U. S. Geol. Survey, No. 102, 1893. 
