PART I CHAZYAN AND RELATED BRACHIOPODS—COOPER 889 
This species is stated to have been taken from the Lowville formation as well as from the 
Leray-Rockland beds. 
R. alternata platys Wilson, 1944, p. 162, text fig. 2, No. 1; pl. 1, fig. 10. 
1946, p. 68, text fig. 2, No. 1; pl. 5, fig. 11. 
R. alternata semiquadrata Wilson, 1944, p. 164, text fig. 2, No. 3; pl. 1, fig. 6. 
1946, p. 69, text fig. 2, No. 3; pl. 5, fig. 7. 
R. alternata transversa Wilson, 1944, p. 165, text fig. 1, No. 6; pl. 1, fig. 11. 
1946, p. 60, text fig. 1, No. 6; pl. 5, fig. 12. 
R. esmondensis borealis Wilson, 1944, p. 169, text fig. 4, No. 1; pl. 1, fig. 8. 
1946, p. 72, text fig. 4, No. 1; pl. 5, fig. 9. 
R. hullensis Wilson, 1944, p. 170, text fig. 4, No. 6; pl. 1, fig. 19. 
1946, p. 73, text fig. 4, No. 6; pl. 5, fig. 20. 
R. opeongoensis Wilson, 1944, p. 171, text fig. 5, No. 5; pl. 1, fig. 16. 
1946, p. 73, text fig. 5, No. 5; pl. 5, fig. 17. 
R. orleansensis Wilson, 1944, p. 171, text fig. 5, No. 6; pl. 1, fig. 13. 
1946, p. 74, text fig. 5, No. 6; pl. 5, fig. 14. 
R. rotunda Wilson, 1944, p. 174, text fig. 5, No. 4; pl. 1, fig. 7. 
1946, p. 75, text fig. 5, No. 4; pl. 5, fig. 8. 
R. subtrigonalis Wilson, 1944, p. 175, text fig. 4, No. 4; pl. 1, fig. 15. 
1946, p. 76, text fig. 4, No. 4; pl. 5, fig. 16. 
R. miodeltoidea Wilson, 1944, p. 179, text fig. 8, No. 2; pl. 2, fig. 9. 
1946, p. 79, text fig. 8, No. 2; pl. 6, fig. 9. 
R. okulitchi Wilson, 1944, p. 181, text fig. 7, No. 2; pl. 2, fig. 7. 
1946, p. 80, text fig. 7, No. 2; pl. 6, fig. 7. 
R. praedeltoidea Wilson, 1944, p. 183, text fig. 8, No. 3; pl. 2, fig. 11. 
1946, p. 81, text fig. 8, No. 3; pl. 6, fig. 11. 
R. semicircularis minor Wilson, 1944, p. 186, text fig. 6, No. 1; pl. 2, fig. 3. 
1946, p. 83, text fig. 6, No. 1; pl. 6, fig. 3. 
COLAPTOMENA Cooper, new genus 
(Greek colapto, chisel; mene, crescent) 
Shells large, attaining a length and width of nearly 2 inches; planoconvex to 
perceptibly concavo-convex ; valves strongly compressed and strongly suggesting 
Leptostrophia in profile and general form. Surface costellate, costellae alternat- 
ing strong and fine; concentric fila strong; posterior margins marked by strong, 
oblique wrinkles. Pseudopunctate, the pseudopunctae closely matted and fine. 
Interior of pedicle valve with pseudodeltidium obsolete; muscle area large, 
subcircular ; diductor scars subflabellate ; adductor field located in the posterior 
of the muscle field, marked by 2 low ridges separated by a narrow groove; pallial 
marks prominent ; vascula media splitting at the anteromedian end of the diductor 
scar, splitting into 3 trunks, I extending directly toward the anterior, the second 
anterolaterally, and a third directed posterolaterally. 
Brachial interior with narrow, subcarinate chilidium; cardinal process large 
and stout ; adductor scars located on each side of a short, rounded median ridge, 
the outer scars being the larger. 
Genotype.—Colaptomena lepiostrophoidea Cooper, new species. 
Discussion.—This genus is most like Rafinesquina and is probably a lateral 
divergence from that genus. It differs from Rafinesquina in the pedicle valve not 
being marked by the single enlarged and elevated median rib so common in the 
