90 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I48 



Fig. 6. Lateral view of a small, incomplete, right valve showing broad plicae 

 and short smooth stage. A paratype from the Mancos Shale, Socorro 

 County, N. Mex. (locality 66, U.S.G.S. D2042) ; U.S.N.M. 132264. 



Fig. 7. Lateral view of a small, unusually curved right valve with recurved 

 beak and umbo, short smooth stage limited to umbo, and typical plicae. 

 A paratype from the Colorado Group (Mancos Shale?), Carthage, 

 N. Mex. (locality 64, U.S.G.S. 3297) ; U.S.N.M. 132262. 



Fig. 8. Lateral view of an adult right valve similar in shape to those of 

 L. bellaplicata bellaplicata, but with a much shorter smooth umbonal area. 

 Note coarse lamellae, characteristic plicae. A paratype from the Colorado 

 Group (Mancos) at Carthage, N. Mex. (locality 63, U.S.G.S. 3295) ; 

 U.S.N.M. 132265. 



Fig. 9. Lateral view of a right valve with reverse inclination (opisthocline) 

 and enlarged anterior auricle. Note broad plicae, short smooth stage 

 limited to umbo. A paratype from the Mancos Shale, zone of 

 Collignoniceras hyatti, Socorro County, N. Mex. (locality 66, U.S.G.S. 

 D2042) ; U.S.N.M. 132266. 



Fig. 10. Lateral view of a left valve, characteristic of the subspecies. Note 

 broad plicae, few in number, broad posterior auricular sulcus, inclination 

 of posterodorsal margin. The holotype, from a massive sandstone in the 

 Mancos Shale, zone of Collignoniceras hyatti, Socorro County, N. Mex. 

 (locality 66, U.S.G.S. D2042) ; U.S.N.M. 132267. 



Fig. 11. Lateral view of a left valve with narrow plicae, otherwise typical 

 of the subspecies ; a paratype from the septarian limestone concretion 

 zone, upper Blue Hill Shale Member, Huerfano Park, Colo, (locality 62, 

 U.S.G.S. 738) ; U.S.N.M. 22012. 



Fig. 12. Lateral view of a left valve with narrow ribs, or plicae, occurring 

 along with normal individuals of the subspecies in the Mancos Shale near 

 Carthage, N. Mex. (locality 63, U.S.G.S. 3295). Compare this with 

 figure 11, from the Blue Hill Shale Member, Huerfano Park, Colo. A 

 paratype, U.S.N.M. 132268. 



Fig. 13. Lateral view of an unusually broad variant of the subspecies from 

 the Blue Hill Shale Member, Huerfano Park, Colo, (locality 69), closely 

 comparable to marginal variants of L. bellaplicata bellaplicata from the 

 Codell Sandstone in the same area (see pi. 6, fig. 15). A paratype; 

 U.S.N.M. 132269. 



Fig. 14. Lateral view of a high left valve with reduced posterior auricle; 

 paratype from the Mancos Shale at Carthage, N. Mex. (locality 65, 

 U.S.G.S. 5303) ; U.S.N.M. 132270. 



Fig. 15. Lateral view of an exfoliated left valve, showing characteristic 

 outline and radial ornamentation; a paratype from the Mancos Shale at 

 Carthage, N. Mex. (locality 64, U.S.G.S. 3297) ; U.S.N.M. 132271. 



Fig. 16. Lateral view of a robust left valve, characteristic of the subspecies ; a 

 paratype from the Mancos Shale, zone of Collignoniceras hyatti, Socorro 

 County, N. Mex. (locality 66, U.S.G.S. D2042) ; U.S.N.M. 132272. 



Fig. 17. Lateral view of a left valve with posterior auricle larger than normal 

 and density of plicae approaching that of L. bellaplicata bellaplicata; a 

 paratype from the Mancos Shale, Carthage, N. Mex. (locality 65, 

 U.S.G.S. 5303) ; U.S.N.M. 132273. 



