Late Pliocene; Extinct.
Southern Florida to South Carolina.
Original Description (from Mansfield, 1932, p. 48-49):
"Shell large, orbicular, moderately ventricose, equivalve, and nearly equilateral, the posterior region being slightly more produced. Sculptured with broad, nearly flat, weakly undulating ribs (seven on the left valve and eight on the right) separated by little wider interspaces. The ribs are broader over the middle of the disk and narrower on each side. Top of ribs sculptured with five to eight coarse, raised threads separated by narrower interspaces. Spaces between major ribs marked with three to five coarse, weakly undulating threads and occasionally with a finer thread. Submargins sculptured with six to eight radial threads, which are equal in strength to the intercostal threads. Ears ornamented with rather coarse radiating riblets.
Dimensions: Holotype (catalogue No, 371326, U. S. Nat. Mus.), left valve, length, 142 millimeters; height, 125 millimeters. Paratype, right valve (catalogue No. 371327, U. S. Nat. Mus.), length, 100 millimeters; height, 104 millimeters.
Type locality: Station 1/1176, Tamiami Trail, about 11 miles east by north of Marco, Collier County, Fla.
The subspecies differs from Pecten (Nodipecten) pittieri Dall, a species collected from Moin Hill, near Port Limon, Costa Kica, horizon a, in having a more ventricose shell which is ornamented with wider and fewer (by two) ribs. The surface of the ribs on the subspecies, although slightly corroded, does not distinctly indicate the vaulted scales, which are strongly developed on the left valve of P. pittieri. Dall, in his original description of P. pittieri, placed it in the section Lyropecten, but it appears to be more closely related to the section Nodipecten than to Lyropecten.
Pecten pittieri Dall and the new subspecies appear to be more closely related to Pecten (Nodipecten) nodosus Linnaeus, of the east coast, than to Pecten (Nodipecten) subnodosus Sowerby, of the west coast.
The new subspecies appears to be an intermediate form between Pecten pittieri and Pecten nodosus.
Pecten (Nodipecten) veatchii Gabb, a Pliocene species from Cerros Island, off Lower California, appears from the illustration to be closely related to my new subspecies.
Occurrence: Pliocene. Station 1/1176 (type locality, 2 valves), station 1/1180 (paratype locality, 1 valve), and station 1/1178 (2 valves)."
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