IO SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I49 



Genus WHITFIELDELLA Hall and Clarke, 1893 



Whitfieldellaf sp. 



Plate 2, figures 14, 17, 19 

 Plate 3, figures 6-10, 14, 17, 20 



Discussion. — A large broken specimen and possibly a dozen clearly 

 immature ones may be referable to Whitfieldella. All are characterized 

 by a smooth exterior, oval outline, and biconvex profile. The single 

 large specimen is a broken brachial valve in which there is a very 

 strong median septum originating beneath a divided hinge plate with 

 stout crural bases. There is no cardinal process. What appears to be 

 a subcircular visceral area is actually related to growth of the shell 

 as shown by comparison with the exterior of the valve. More than 

 one species, perhaps more than one genus, is represented by the small 

 specimens. Some are elongate oval while others are almost pentagonal 

 and as wide as long. Some may be young individuals of the species 

 here referred to as Camerellaf. 



Additional complete mature valves are needed to determine the 

 correct taxonomic position of these specimens. 



Figured specimens.— USNM 145343, 145349, 145350, 145351. 



Superfamily PLECTAMBONITACEA Cooper and Williams, 1952 

 Genus ANOPTAMBONITES Williams, 1962 



In the collections from Hard Luck Creek are several specimens 

 that are obviously closely related to Leptella? grayae, a species origi- 

 nally illustrated by Davidson (1883, p. 171) partly under two names, 

 Leptaena grayae and Leptaena llandeiloensis. As pointed out by Reed 

 (1917, pp. 873-874) Davidson included the interior of L. grayae 

 (1883, pi. 12, figs. 27a, b) as L. llandeiloensis. Jones (1928, p. 489) 

 showed that one of the specimens illustrated by Reed (1917, pi. 13, 

 fig. 14) should be excluded from L. grayae. 



Jones included L. grayae in his genus Leptelloidea (1928, pp. 385- 

 389, 399-400) although it differs from all other species in the genus 

 in lack of convexity and "undifferentiated surface ornamentation." 



Opik (1930, pp. 132-133; 1933, pp. 30-32) revised the genus Lep- 

 telloidea using the characters of the diaphragm in the brachial valve 

 as the most important features. This resulted in a somewhat different 

 grouping of species than that proposed by Jones. Opik tended to agree 

 with Reed that L. grayae probably belonged in Leptella Hall and 

 Clarke, although at the time that genus was too imperfectly known for 

 anyone to be sure how it should be classified relative to Leptelloidea. 



