Cerion clenchi Gould & Woodruff, 1986
"MORPHOLOGY: The general shape of Cerion clenchi easily distinguishes this taxon from all other New Providence cerions, for it has the smoothest and most continuous outline of any Cerion we have seen. From a fairly triangular apex (signifying a relatively high protoconch), it expands evenly and regularly in width, reaching a maximum two to three whorls from the aperture, unlike C. glans, which expands earlier near the top of the spire. From this maximum, width tapers gradually and evenly until deposition of the aperture. Thus, Cerion elenchi presents an almost perfect "barrel" shape in outline, with maximum width at about the spire's midpoint. By contrast, C. agassizi, with its triangular outline, tends to be widest near the aperture, while C. glans and C. gubernatorium are widest nearer the spire and not nearly so regular in expansion and contraction to and from the point of maximum width.
Ribbing also distinguishes C. elenchi from other New Providence Cerions, for it displays remarkably even ribs of medium strength and constant intensity throughout growth. Most samples deposit about 40-45 ribs per whorl in the middle part of the spire, compared with 20-25 for C. glans and 50-60 for C. gubernatorium. Most C. agassizi samples are smooth or, if ribbed, deposit fewer, coarser ribs, as in C. glans. But number of ribs is not the most distinctive character of ornamentation in C. clenchi. Rather, the close and, even spacing and constant strength of ribbing impart an unusual regularity and consistency of appearance to the shell. By contrast, ribs of C. glans and C. agassizi are always spaced
more irregularly, and exhibit more variability in strength. These two features combinedthe remarkably smooth and barrel-shaped outline and the regularity of ribbing-give to C. clenchi a most unusual appearance of continuous and elegant form for a Cerion.
In size, most C. clenchi samples are intermediate between large C. agassizi and the
smaller C. glans and C. gubernatorium of modern New Providence. They are higher (though not necessarily wider) than C. glans and C. gubernatorium and grow more whorls. The holotype (from locality 105 on the prominent ridge south of Oakes Field Airport) has 91/8 postprotoconch whorls, and is 30.3 mm high and 11.8 mm wide (fig. 38)-an average specimen for this sample of average size (compare these values with means for C. glans and C. gubernatorium in table 9). A few samples, however, contain shells of smaller average size, and within the range of mean C. glans and C. gubernatorium.
The aperture of C. clenchi is strong, relatively thick lipped and recurved, but not otherwise distinctive. The umbilicus tends to be relatively narrow, as we would expect for a shell that reduces in width before depositing its aperture.
TEMPORAL DISTRIBUTION: Exclusively in fossil soils and eolianites of the oldest of three stratigraphic units of New Providence (Garrett and Gould, 1984). No other Cerion species occurs in these deposits, and C. elenchi has been found nowhere else on the island. We are pleased to report that C. clenchi also occurs in the stratigraphically oldest dunes of
both Eleuthera and Cat Island, thus confirming this criterion and extending the species' range. On New Providence, C. clenchi has been collected at Blue Hills (type locality the dune ridge south of Oakes Airfield), at the base of, and stratigraphically below, hills containing C. agassizi in their higher units at Prospect Ridge, Fort Charlotte, and the dune ridge running from the caves east of Gambier, through Gambier to Old Fort Point.
ETYMOLOGY: We are pleased to name this species to honor the memory of Bill Clench, the grand old man of Cerion studies. His careful, descriptive work on Bahamian Cerion, and his incomparable curation of the Cerion collection in the Department of Mollusks at the Museum of Comparative Zoology for 40 years, have formed the sine qua non of all our work. He did most of his field work during the 1930s under arduous conditions, spending days on the mailboats plying among islands, while we happily fly from place to place. It seems fitting that the oldest Cerion of New Providence, the basal form of the island, be named to honor the memory of this leader in Cerion studies.
A certain irony has not escaped our notice: we have labored so long in this work to convince readers that the modern Cerion fauna of New Providence contains but two slightly different, though clearly distinguished, taxa. The fossil record, with its three units, each with a distinctive Cerion fauna, is much richer, even though no evolutionary connections can be drawn among these faunas. The modern distinction of C. glans from C. gubernatorium almost becomes an epiphenomenon upon this richness, but a fascinating epiphenomenon in its own right-and the key, we think, to a taxonomic resolution of all modern Cerion in the Bahama Islands.
HOLOTYPE: Collection of fossil invertebrates M.C.Z. No. 29186." (Gould and Woodruff, 1986:482-483)