Chesapecten jeffersonius (Say, 1824)
SAY, T. 1824. An account of some of the fossil shells of Maryland. Journal of the Academy of Natural Sciences of Philadelphia, 4 (1): 124-155. [p. 133, pl. 9, fig. 1]
1824 Pecten jeffersonius Say, 1824
T. Say, 1824, plate 9.
|
«P. Jeffersonius. Pl. ix. fig. 1. Subequivalve, with from nine to eleven striated ribs.
Description. Shell rounded, convex, not quite equivalved, one of the valves being a little more convex than the other; the whole surface covered with approximate, scaly strire: ribs elevated., rounded, with six or seven striae on the back of each; intervening grooves profound: ears equal; sinus of the ear of the superior valve, not profound, being barely one eighth part of the length of the ear: within with broad rounded flattened ribs. Length five inches and three-tenths, breadth five inches and seven-tenths. Specimens of this truly fine shell are not uncommon. The Academy has been long in possession of several single valves, in an excellent state of preservation, obtained by my friend Mr. J. Gilliams, and others which were presented by Mr. Watson, who purchased them at the sale of the collection of the late Professor Barton. Mr. Finch has succeeded in obtaining entire specimens of the two valves of the same individual. I am of the opinion that Lister's plate 167, is intended to represent this shell, and that the singular appearance of the marginal striae in that figure is a deviation from the ordinary formation of the species, and is owing to the dislocation of the lines of increment, and obliteration of the longitudinal striae. Lister describes his specimens to be of a "blue-clay colour," in this respect perfectly corresponding with two specimens before me.» THOMAS SAY, 1824
|
«Occurrence.— The type locality is Virginia, probably from the James River near City Point or the York River at Yorktown. Additional Virginia localities (Yorktown Formation Zone 1 of Mansfield) include 2 miles (3.2 km) below Grays Point Bridge on the Rappahannock River (fig. 1, loc. 34; USGS loc. 25323), Glebe Neck (beach to +3 ft (1 m)) (fig. 1, loc. 35; USGS loc. 25324), Mouth of Felgate's Creek (at beach level) (fig. 1, loc. 36; USGS loc. 25325), Zone 1 Yorktown Formation (of Mansfield) from Chippokes Creek to Grove Wharf (beach to +5 ft (1.5 m)) (fig. 1, loc. 37; USGS loc. 25326), and Delaware at rte. 671 bridge over Nottoway (lower 1.5 ft (0.5 m)) (fig. 1, loc. 38; USGS loc. 25327).
Comparison and remarks.— Chesapecten jeffersonius differs from C. septenarius in having more plicae (usually 9 to 12 as opposed to approximately 6 or 7) , which are less broadened, less flattened on the summits, and less square sided, with the exterior covered with less coarse scabrous sculpture. Chesapecten jeffersonius differs from C. madisonius in having more convex valves, in having fewer and more elevated plicae; also, in the exterior sculpture being less "beaded" in appearance, and in the interior ribbing being expressed in the adductor muscle region. The following information (the title and the abstracted text) was given by Huddesford (1770) in a new edition of Lister's publications. A translation of Lister's original Latin description (Lister, 1687, p. 69) is as follows: By far the largest of all scallops presented with 8 or 10 ridges at the highest point and similarly deep grooves.
It should be noted that there was no separate text for each figure, but that the entire description was included with each figure (as reproduced in pl. 1). A probable syntype of C. jeffersonius was obtained from the British Museum, the repository of of the fossil material which J. Finch loaned Say to describe. This specimen agrees with Say's figure in size, although the details of sculpture are apparently artistically generalized possibly from several specimens (synthetograph). This articulated specimen from the British Museum is here designated as the lectotype.» WARD, L. W. & B. W. BLACKWELDER. 1975. Chesapecten, a new genus of Pectinidae (Mollusca: Bivalvia) from the Miocene and Pliocene of eastern North America. United States Geological Survey Professional Paper, 861: 1-24, pls 1-7 [p. 15]
|
Reproduction of the illustration of the earliest figured and described fossil from America, from Lister's (1687) Historiae Conchyliorum Liber III; L. W. Ward & B. W. Blackwelder, 1975, Chesapecten, a new genus of Pectinidae, plate 1.
Chesapecten jeffersonius (Say); L. W. Ward & B. W. Blackwelder, 1975, Chesapecten, a new genus of Pectinidae, plate 2, figures 1-3; plate 5, figures 3-7; plate 7, figures 3, 10.
|