"Chlamys" clinchfieldensis (Harris, 1951)
HARRIS, G. D. 1951. Preliminary notes on Ocala Bivalves. Bulletins of American Paleontology, 33 (138): 224-273, pls. 30-42. [p. 228, pl. 33 (4), figs. 4-7; pl 34 (5), figs. 1, 1']
1951 Chlamys spillmani var. clinchfieldensis Harris, 1951
G. D. Harris, 1951, plates 33 (4)
and 34 (5). |
«The use of Gabb's name spillmani has already been discussed (Bull. Amer. Paleont., 30: p. 27, pl. 6, figs. 3-8). Plate 6, figures 3 and 4 of this 1946 work illustrate the common appearance of the species. The sculpturing, however, is rarely so pronounced as indicated by figure 5 of the same plate.
Well-preserved details of Ocala specimens are herewith shown as figures 1-3, Plate 4. The central beaded ridge of each rib is more pronounced than the lateral ridges (if present). On the earlier part of the shell, the ribs appear generally quite smooth. As the shell increases in size, the ribs are more granulated. In adult shells lateral ridges or terraces generally become clearly developed. Concentric lines in crossing these ridges may show pronounced outgrowths [see these Bulletins, 30: pi. 6, figs. 5-8). Nuperus, perplanus and spillmani each have a preponderance of one type of ornamentation, but each may borrow one or more characteristics from the other members of the trio. Some specimens at typical Ocala localities, as at Sta. 1167 or 1181, are much larger than the common Shubuta representatives. They may reach a width of 55 mm. The ribs and interspaced on these larger specimens appear smooth to the naked eye, thus seeming to preclude close spillmani relationship. In the case of those large forms where the side slopes of certain ribs have microscopic concentric lines, although the apex of each rib may be perfectly smooth (Pl. 4, fig. 6), the varietal name clinchfieldensis may properly be applied. Between such large forms and the Shubuta representatives there are intermediate ones with clearly defined spillmani characteristics. Occurrence.-- Spillmani is one of the most common of bivalve species from the Ocala limestone of Georgia and Florida. See Stas. 1167, 1168, 1170, 1172, 1173, 1176, 1181.» GILBERT DENNISON HARRIS, 1951
|
«DIAGNOSIS.— Populations of the C. clinchfieldensis stock containing smooth and multilirate-ribbed forms in which 25 percent or more of the individuals have smooth ribs prior to the 25 mm-in-height growth stage. It differs from Chlamys nupera (Conrad) in lacking faint lirations on the ribs and interspaces prior to the 25 mm-in-height growth stage.
DESCRIPTION.— Shell orbicular, moderately thick; small; maximum height 45.6 mm (mean height 27.9 mm); nearly equally convex valves; hinge line slightly concave in right valve, nearly straight in left valve; ribs fairly high, rounded, usually smooth, occasionally with lirae near the ventral margin; ribs as wide as interspaces; right and left valves with 21 to 25 ribs (mean 22.4); lirae develop in pairs on opposite sides of ribs and may extend into interspaces; concentric lamellae closely spaced and slightly sinuous in adult part of disk. Ears fairly large, subequal, anterior portion longer than posterior portion, prominently striated with 4 to 6 radial threads on the anterior ear, 4 to 7 radial threads on the posterior ear; byssal notch deep; ctenolium with 2 or 3 teeth. Hinge with provinculum, 1 or 2 pairs of cardinal crura; resilial pit rather small with lateral ridges in the right valve. Interior of valves with faint internal ribs fluted along the ventral margin. DIMENSIONS.— Holotype (Paleontological Research Institution, Ithaca, New York) from Pennsylvania Cement Corporation Plant 2, Clinchfield quarry (now Medusa Portland Cement Co.), Clinchfield, Georgia, right valve: height 47 mm, length 46 mm (fide Mrs. K. V. W. Palmer, personal communication, December 31,1973). OCCURRENCE IN GEORGIA.— Chlamys clinchfieldensis is common in the Clinchfield Sand and the Ocala Limestone at Rich Hill, abandoned quarry located between Knoxville and Byron (locality 34); common in the Clinchfield Sand and Ocala Limestone at Area 22 kaolin pit, Huber (locality 35); rare in Clinchfield Sand and Ocala Limestone at Georgia Rock Products Company quarry near Arlington (locality 24); common in the Clinchfield Sand at the Georgia Kaolin Co. mine near Gordon (locality 36); and common in the Clinchfield Sand and lower part of the Ocala Limestone at the Medusa Portland Cement Company quarry near Clinchfield (locality 29). DISTRIBUTION ELSEWHERE IN THE SOUTHEASTERN UNITED STATES.— Chlamys clinchfieldensis is known from Moodys Branch Marl (Upper Eocene) localities across the state of Alabama. It is rare at Double Bridges Creek, about 8 miles north of Geneva (locality 19), common in a road cut about 2 miles west of Silas (locality 7), and common in a road cut 3.9 miles west of Gilbertown, Alabama (locality 6). REMARKS.— Because of the evolutionary development of liration on the ribs in C. clinchfieldensis, shells from older beds generally will have all smooth ribs. Samples of shells from younger beds will not only have a larger proportion of specimens with lirae on the ribs, but the average development of lirae will appear at an earlier growth stage.» GLAWE, L. N. 1974. Upper Eocene and Oligocene Pectinidae of Georgia and their stratigraphic significance. Geological Survey of Georgia, Information Circular, 46: 1-27, pls. 1-4. [p. 4]
|
Chlamys (Aequipecten) clinchfieldensis Harris; L. N. Glawe, 1974, Upper Eocene and Oligocene Pectinidae of Georgia and their stratigraphic significance, plate 1, figures 7-9; plate 2, figures 6, 9.
|
«The Clinchfield Sand in the area under consideration contains a megafauna very similar to that of the Ocala Limestone. The echinoids Periarchus lyelli, P. lyelli pileus-sinensis, and Laganum floridanus have been observed in this unit, generally in the limy beds at the top. The characteristic Ocala pecten Chlamys spillmani clinchfieldensis is common locally in the Clinchfield, generally in the more calcareous portions. An oyster which Stenzel (personal communication) identified as Crassostrea gigantissima occurs at the top of the Clinchfield but not in the overlying Ocala. Shark, stingray, porpoise, whale, and sawfish teeth, along with whale and manatee bones are abundant in the Clinchfield at localities 9 and 10.»
PICKERING, S. M., JR. 1970. Stratigraphy, paleontology, and economic geology of portions of Perry and Cochran Quadrangles, Georgia. Georgia Geological Survey Bulletin, 81: 1-67, pls. 1, 2, Appendix A, B. [p. 25]
|
Chlamys spillmani clinchfieldensis; S. M. Pickering Jr., 1970, Stratigraphy, paleontology, and economic geology of portions of Perry and Cochran Quadrangles, illustrations from Appendix A.
|