NATURAL SCIENCES OF PHILADELPHIA. 
291 
1. M. (Myoconclia) incurva, C., Miocene, Foss. 52, 28, 1. 
2. M. (Mytilus) incrass at a, C., ib., 74, 42, 4. 
PE CTENIDJE. 
PECTEN, Lin. 
P. fraternus. — Ovate, upper valve slightly ventricose, lower convex 
depressed; ribs 15 or 16, prominent; convex, laterally flattened, nar- 
rower than the interstices, trilineate, squamose ; interstices with fine, unequal, 
delicately squamose radiating lines ; lower valve, ribs broader, and more nu- 
merously lined ; ears moderate, with radiating numerous rugose lines. 
Locality . Virginia. (Miocene.) 
Differs from P. Jeffersonius in being comparatively more elevated or ovate ; 
in having smaller ears, and more numerous and narrower ribs, &c. 
P. Edgecomens is. — Suborbicular ; height not quite equal to the length ; 
lower valve-ribs 16 to 17, prominent, but not elevated, square or convex- 
depressed, not quite as wide as the intervening spaces, radiately lined with 
finely squamose strise, most conspicuous towards the margins, interstices of 
ribs carinated, in the middle squamose and finely striated ; ears with fine close 
unequal squamose radiating lines, the larger ones most prominent on the pos- 
terior side ; margins of ligament pit carinated. 
Locality. Edgewood Co., North Carolina. Cab. Smithsonian Institution. 
Allied to P. eboreus ; the carina between the ribs distinguish it from that 
species. (Miocene.) 
LYROPECTEN, Conrad. 
Inequivalve, radiately costate; hinge with a triangular pit as inPeeten 
and diverging prominent teeth on each side the ligament cavity. 
Lyropectin (Pallium) estrellanus, C., Pacific R. R. Reports, 1855, vi. 
pi. 3, f. 15. 
This genus is peculiar to the Miocene of the Pacific slope, and appears in 
three large species, the second of which has been figured and described as 
Pallium estrellanum , in Pacific Railroad Reports, vol. vii. 191, but is very dis- 
tinct from that species. I propose to name it Volcefonnis. 
L. cr ass icard o. — Suborbicular; ribs 15; larger valve ventricose ; ribs 
rounded, not quite as wide as intervening spaces ; whole surface radiately 
striate with equal lines, about 11 on the ribs and 5 on the interstices ; opposite 
valve convex, ribs prominent, narrower and more abrupt than in the large'" 
valve, disposed to be concentrically nodulous or undulated by broad concen- 
tric furrows, and sometimes an abrupt concentric truncation. 
Locality. California. 
OSTRIADvE. 
OSTREA, Lin. 
0. f'alciformi s. — Falcate, radiately ribbed ; ribs numerous, regular, 
close, rounded, crossed by squamous lines ; ribs small on the anterior de- 
pression ; margins plicated, not crenulated ; ligament cavity oblique. 
Locality. Enterpise, Clark Co., Miss. Dr. Spillman. (Eocene.) 
Revision of the GULLS of North America; based upon specimens in the 
Museum of' the Smithsonian Institution. 
BY ELLIOTT COUES. 
The present paper is an abstract of a more extended Monograph on the 
Gulls of North America, prepared for publication in a Government Report. 
1862 .] 
