42 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I48 



either valve. I conclude from this that the direction of curvature is 

 variable and not rigidly controlled genetically in this species (although 

 posterior curvature dominates). Consistency in the position of the 

 muscle scar and cardinal characters on both valves, irrespective of 

 coiling direction, indicates attachment is always by the left valve, as in 

 other ostreids. 



Stratigraphic and geographic occurrence. — Lopha lugubris ranges 

 through the Juana Lopez Member and its equivalents (zones of 

 Prionocyclus wyomingensis wyomingensis: early Late Turonian, and 

 P. wyomingensis elegans: middle Late Turonian) in central, south- 

 central, and eastern Colorado, western Kansas, and northern New 

 Mexico. The primary types were reported to have come from beds 

 containing P. macombi {P. wyomingensis wyomingensis zone). It 

 has been found at an equivalent level in the Mancos Shale of western 

 Colorado and New Mexico. In Huerfano Park, Colo., fragments 

 questionably referable to this species were collected in the upper part 

 of the "Pugnellus Sandstone" (Codell Sandstone Member, CarHle 

 Shale; upper part of zone of Collignoniceras hyatti) associated with 

 L. hellaplicata bellaplicata. The ranges of these species overlap 

 slightly in Texas also, where L. lugubris is found in the upper 3 feet 

 of the Eagle Ford Shale (late Middle Turonian, upper part of L. bella- 

 plicata bellaplicata zone) and in the overlying conglomeratic calcaren- 

 ite bed between typical Eagle Ford Shale and Austin Chalk. Hattin's 

 report of this species from the Blue Hill Shale Member in Kansas 

 (lower part of zone of Collignoniceras hyatti; 1962, p. 84) is based on 

 a typical specimen of L. lugubris collected by J. B. Reeside, Jr. 

 Pieces of matrix adhering to the specimen are rusty-brown calcarenite 

 characteristic of the Juana Lopez Member in Colorado and at scattered 

 Kansas localities, and the specimen probably came from a higher level 

 than Reeside assumed. I have also examined specimens from the 

 Fairport Chalk Member which Hattin assigned to this species (1962, 

 p. 54). These belong to a distinct lineage and appear most closely 

 related to the younger "Ostrea" tecticosta Gabb. 



Specimens of Lopha lugubris used in this study were obtained from 

 localities 1 through 39 and 48, described in detail at the end of this 

 report. 



Illustrated and measured specimens. — Lectotype, selected by 

 Stanton (1894), U.S.N.M. 9822, the original of Conrad's plate 10, 

 figure 5b (1857); Stanton's hypotypes, reillustrated (1893, pi. 4), 

 U.S.N.M. 22859a (Stanton's fig. 5) 22859b (Stanton's fig. 3), 

 22860a (Stanton's fig. 2) ; Meek's hypotype (1876, pi. 1, fig. la). 



