PANAMIC-PACIFIC PELECYPODA 31 



Indian graves or huacos in coastal Peru are thickly covered or literally 

 snowed under a blanket of whitened shells of D. peruviatia. The Veneridae, 

 with about 62 species, ranks as the largest family of Panamic bivalves, and 

 such species that are sufficiently abundant, are much sought for as food 

 along the entire coast. Perhaps the largest and finest species in the family 

 is Periglypta muLticostata, and in a few places, as in the Pearl Islands, it 

 is sufficiently common to be gathered for food. Another large clam, but 

 rare at most localities, is Ventricolaria isocardia, similar to V. rigida of 

 Florida. Tivela hians is plentiful in northwestern Peru on sandy beaches 

 and is gathered in large numbers by the natives. It is often commensal with 

 a small sea anenome. The genus Hysteroconcha, with but one species in 

 the Caribbean, has four in the Pacific zone, the largest and commonest is 

 H. lupanaria with long spines and usually purplish coloration, while in 

 H. brevispinosa, the spines are short, often reduced to mere stumps, and 

 the color is white. Amongst the Chiones, C. compta, a. large, thick-shelled 

 species, like an overgrown C. cancellata, is most common in the south. In 

 the allied genus Chionopsis are several fine species such as C. amathusia, 

 C. gfiidia, C. jamaniana, and C. ornatissima with highly intricate surface 

 sculpture. Other equally characteristic Panamic venerids are Notochione 

 cokcmbiensis, a thick-walled shell with coarse ribbing and variable color 

 markings and the Nioche asperrima with a fine cancellate sculpture like 

 that seen on some Codakias. Protothaca grata, showing an endless variation 

 in coloration, is collected in quantities from gravel bars exposed at low 

 water along the coast of Ecuador. Dosinia ponderosa, the largest species of 

 the genus and a hangover from the Miocene, is common at many places and 

 ranges throughout the whole province and southward into the Peruvian. 

 The Mactridae have several fine species; HarveUa elegans and Tumbezi- 

 concha trachoides have thin fragile valves marked with strong, concentric 

 or oblique undulations, and appear to range through the entire province 

 wherever suitable conditions of environment occur. Another thin-shelled, 

 fragile species is the Raeta undidata, common along the coast of north- 

 western Peru and ranging far southward into the Peruvian Province; else- 

 wihere the species is rather rare but extends northward to the Gulf of 

 California. Mactrellona alata and M. exoleta, together with M. clisea, are 

 met with along sandy beaches, the two former species also living in the 

 Caribbean region. The Micromactras form a group of several species, often 

 difficult to separate properly from each other. Rock boring mollusks such 

 as the Lithophagas and the Pholadidae are especially common along certain 

 parts of the coast of Ecuador, and in some stretches where the shore is 

 formed of soft rock formations, they thereby contribute substantially to 

 shore line erosion. Amongst the Corbulidae, may be mentioned the 

 large Panmmcorbula inflata with subequal, convex valves, and a hinge 

 showing vestigial lateral teeth; it is found principally in muddy, brackish- 

 water situations. Other interesting species of the family are Caryocorbula 

 ovulata, C. ameystina, Tenuicorbtda tenuis, and the curious Serracorbula 

 tumaca with serrated margins. 



