GEOLOGY AND PALEONTOLOGY OF CANAL ZONE


 Occurrence: Gatuncillo formation (late Eocene), Madden basin, localities 9, 12, 15.
 Genus Pachycrommium Woodring?
 Woodring, Carnegie Inst. Washington Pub. 385, p. 391, 1928. Type (orthotype): Anaura guppyi Gabb, Miocene, Dominican
 Republic.
 Pachycrommium? solenaeum Woodring, n. sp.
 Plate 14, figure 1
 Of medium size, shouldered, moderately inflated. Spire high, turreted. A narrow channel adjoins suture. Aperture short. Sheath narrow, rim low. Posterior part of sheath overlapped by narrow lobe, which becomes low and unrecognizable anteriorly. Umbilicus closed.
 Height (not quite complete) 32.5 mm, diameter (somewhat crushed) 22 mm (type).
 Type: USNM 561364.
 Type locality: 38 (USGS 17166, Rio Casaya area, Quebrada de Oro, a northwestward-flowing tributary of Rio Casaya, 3.3 kilometers southeast of east end of Gamboa bridge, Canal Zone), Gatuncillo formation.
 The type (and only specimen) of this species is a silicified fossil from the Gatuncillo formation. The outline of body whorl and aperture is somewhat distorted by lateral crushing. The replacing silica is granular.
 The generic assignment of this species is doubtful. The type of Pachycrommium has a gently sloping shelf between the suture and the shoulder, and a more elongate aperture. Moreover, sheath and lobe can be distinguished only on immature specimens, the lobe of mature shells forming a wider and more strongly edged everted columellar lip than that of Pachycrommium? solenaeum. Nevertheless a species that appears to be properly referred to Pachycrommium has a channel adjoining the suture and separation of sheath and lobe evidently depends on growth stage. "Amauropsis" burnsii meridionalis Pilsbry (1922, p. 387, pl. 34, figs. 23, 24; Miocene, Dominican Republic), which is discussed under Pachycrommium? ef. P. trinitatensis (p. 97), has a channel adjoining the suture. Lobe and sheath are well defined on the posterior part of the sheath on the only specimen in the U. S. National Museum, but not on the type, according to Pilsbry's illustration.
 Eocene high-spired globularines from America and other regions have been referred to Pachycrommium. It is doubtful, however, how many of them-including species mentioned when the generic name was proposed, as noted by Palmer (1937, p. 136-137)-are closely related to Pachycrommium guppyi.
 Occurrence: Gatuncillo formation (middle Eocene), Rio Casaya area, locality 38.


 Pachycrommium? proinum Woodring, n. sp.
 Plate 15, figure 12
Lupia perovata (Conrad), Dall in Hill, Mus. Comp. Zool.
 Harvard College Bull., v. 28, p. 273, 1898 (list; Eocene, Canal Zone). Brown and Pilsbry, Acad. Nat. Sci. Philadelphia
 Proc., v. 63, p. 360, 1911 (Dall's record).
 Of medium size, shouldered, strongly inflated. Spire,. high, turreted. Whorls sloping from suture to shoulder. Aperture elongate. Sheath narrow, for most part not preserved. Lobe narrow, imperfect. Umbilicus closed. Very faint microscopic spiral lineation visible on some specimens on and near shoulder. Type and two other specimens show narrow retractive dark axial bands.
 Height (incomplete) 26 mm, diameter 19 mm (type). Height (not quite complete) 35 mm, diameter 22 mm.
 Type: USNM 135200.
 Type locality: 40a (USGS 2683, Vamos Vamos, off Palenquilla Point, Canal Zone, now submerged),' marine member of Bohio(?) formation.
 Though this globularine is represented by 15 specimens collected at Vamos Vamos and at locality 41 near Plaenquilla Point, none completely shows the columellar lip. The lobe is shown on five specimens, on all of which it is narrow, and an imperfect narrow sheath is visible on the type. Dark axial bands are well shownon the body whorl of three specimens. They may possibly indicate axial bands differing in shell texture rather than color bands.
 Incomplete as these fossils are, they suggest a Pachycrommium that is less inflated than P. guppyi and has whorls characterized by a steeper slope between the suture and the shoulder.
 Dall identified this globularine as the Claiborne (middle Eocene) species "Lupia" perovata (Conrad), an identification that doubtless had much influence on his conclusion that the strata at Vamos Vamos, and by inference at Gatun, are Eocene. "Lupia" perovata has a higher less turreted spire. In outline of whorls Pachycrommium? proinum is more similar to the Jackson (late Eocene) species "Amauropsis" jackssonensis Harris, which, like "Lupia" perovata, has a higher spire. Mansfield's (1940, p. 222, pl. 27, fig. 44) late Oligocene Pachycrommium sp., from the lower part of the Chickasawhay marl of Alabama, is less inflated than the species from Panama and has a higher spire.
 Pachycrommium? proinum is closely related to Pseudocrommium gabrielensis Clark (Clark and Durham, 1946, p. 19, pl. 16, figs. 14, 15), from the late Eocene of Colombia, but is smaller and has a more turreted spire. The paratype of Pseudocrommium gabrielensis has indistinct alternating dark and light axial bands. Pseudocrommium carmenensis Clark (Clark and Durham, 1946, p. 19, pl. 16, fig. 7) evidently is conspecific with P. gabrielensis.


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