22 
MUSEUM BULLETIN No. 31. 
Rafimsquina precursor sp. nov, 
Plate VII, figure 5. 
Leptwna altemata Hall ( partim ). Pal. N.Y., 1847, 1, Pl. 81A, figs, 
lf-lh. 
This form, allied to Rafinesquina deltoidea, deserves recognition 
because of stratigraphic value. It is found in the upper Prasopora 
beds and indicates the approach to the Rafinesquina deltoidea beds at 
Trenton Falls; in Ontario it is found in the Prasopora beds, along 
with Remopleurides , Amphilichas trentonensis , and other species 
which are believed to hold a position just below the base of the true 
"deltoidea” beds. 
This variety is triangular in shape and somewhat nasute in front. 
The surface is covered with alternating striae, one or two fine ones 
between each pair of coarse ones. It differs from R. deltoidea in hav- 
ing less of a flattened area on the valves, in having the geniculation 
near the middle and less abrupt, and in the total lack of the concen- 
tric wrinkles which are usually so characteristic of that shell, but 
which are sometimes almost or quite lacking. 
Horizon and Locality . Found in the upper part of the Praso- 
pora beds at Trenton Falls, N.Y., and at Trenton, Ont., where the 
holotype was collected by E. J. Whittaker and the writer. 
Genus, Strophomena Bl'ainvllle. 
Strophomena trilobata (Owen). / 
Plate VII, figure 6. 
Lepicena trilobata Owen. Geol. Surv. Wis., Iowa, and Minn., 1852, p. 
584, PI. 2, figs. 17, 18. 
Strophomena trilobata Miller. Am. Pal. Foss., 1877, p. 138. Lesley, 
Diet. Foss., Penna., 1890, p. 1134, figs. 12, 13, Winchell and 
SchuchertjPaL Minn., 3, 1893, p. 395, PL 31, figs. 12, 13. White- 
aves, Pal. Foss. Can., 3, pt. 3, 1897, pp. 139, 241. Grabau and 
Shimer, N. A. Index Foss., 1, 1907, p. 223, figs* 271 g, h, 
Strophomena fiuciuosa Billings (partim). Pal. Foss. Can., 1, 1865, 
p. 123. (Not the specimen figured.) 
Specimens of this species are figured because the writer at one 
time believed it to be a new species, and, to his regret, his manuscript 
name for it has appeared in print. 1 The shell is exceedingly like 
iGeol. Surv., Can., Sum. Kept., 1912, p. 297 (correctly listed on p. 
3461 . 
