398 American Seashells 



2 to 3/4 inches in height, elongate, with 32 to 35 mostly smooth ribs. 

 The ribs at the posterior end have small, tooth-like scales. Middle ribs com- 

 pletely smooth and squarish. Externally light-cream with irregular patches 

 of reddish brown. Interior china-white with the deepest part flushed with 

 orange-buff. As a rule, the posterior margin is pale-yellow, merging into 

 pale-purple at the extreme edge. A West Indian species which has been 

 found on the most southerly keys. 



Tr achy car dium quadra genariurn Conrad Giant Pacific Cockle 



Plate 31a 



Santa Barbara to Lower California. 



3 to 6 inches in size, commonly slightly higher than long, inflated, and 

 with 41 to 44 strong, closely set, squarish, radial ribs which bear small, up- 

 right, strong, triangular spines, especially at the anterior, posterior and ventral 

 portions of the shell. Ribs on beaks smoothish. Exterior whitish tan, but 

 commonly covered with a thin, opaque-brown periostracum. Interior dull- 

 white. Moderately common from shore to 75 fathoms. Known locally as 

 the Spiny Cockle. 



Genus Papyridea Swainson 1840 

 Papyridea soleniformis Bruguiere Spiny Paper Cockle 



Plate 39n 



North Carolina to south half of Florida and the West Indies. 



I to 1% inches in length, fairly fragile, moderately compressed, and 

 gaping posteriorly where the margin of the valve is strongly denticulated 

 by the ends of the dozen radial, finely spinose ribs. Exterior tawny with 

 rose flecks or mottlings. Interior glossy, mottled with violet and white, 

 rarely a solid pastel-orange. Moderately common from low tide to several 

 fathoms. The name hiatus Meuschen used for this species in ]olmsonia is 

 not valid (ruled non-binomial). 



A similar species, P. semisulcata Sowerby (Frilled Paper Cockle, pi. 32c) 

 found from low water to 40 fathoms from southern Florida to the West 

 Indies, is less than y-> inch in length, white, twice as fat, and with longer 

 denticulations at the end of the 12 to 15 radial ribs. Uncommon, except off 

 Miami where it is commonly dredged. 



Subjamily FRAGINAE 

 Genus Trig07iwcardia Dall 1900 



Trigojiiocardia media Linnc Atlantic Strawberry Cockle 



Plate 39m 



North Carolina to southeast Florida and the West Indies. 



