446 NATUKAL HISTORY OF HAWAII. 



and a fossil species. It has its firm .shell sculptured with a large number of 

 radiating riblets, and the margin minutely roughened or crenulated. 



The genus Cytherea is represented by a heart-shaped clam-^ that is sim- 

 ilar to the Venus clam but is much rounder and thicker. Like it, the hinge 

 has three strong teeth, but the species has its surface beautifully marked with 

 radiating blotches of brown. These markings, however, often disappear from 

 beach-worn specimens, or in old age, leaving the pure white shell slightly 

 roughened with minute hair-like growth lines. The markings are responsible 

 for the common name tent or encampment shell. 



In Hawaii, as elsewhere, one of the commonest forms of clam shell everywhere 

 along the beach is a species of Venus -■* or round clams. Its stout white 

 shell is beautifully roughened by prominent concentric bands which are 

 broken up into numerous rectangular spaces by the radiating rib-like lines. 



The typical species of Cardium or heart .shell -° found on Oahu is easily 

 identified by its heart shape when both valves are joined, and by the strongly 

 convex valves, which are deeply ribbed, the ribs interlocking on the margin of 

 the shell. In addition to the center teeth there is also a strong tooth at the 

 extreme end of the hinge line. The inner surface shows the furrows of the 

 rib lines, and even in beach-worn specimens it is of a delicate pink color. 



Several species belonging to the family of rock oysters -'^ are found on 

 the beaches, as they are fond of attaching themselves to various ob.jects, 

 especially the dead and growing coral. At first glance they may be mistaken 

 for oyster shells, but their thick, heavy, solid, foliated shell is somewhat spiral 

 at the tip and the unequal valves are united by teeth, two in the left, or at- 

 tached valve, and one in the upper, or lid valve. The name of the genus -'' 

 has reference to their gaping appearance. Some of the specimens are four 

 inches in length and the two valves together often weigh a pound. The inside 

 of the shell may be white or colored, especially about the margin, with rose, 

 lavender or brown. As they are very thick and strong, they long withstand 

 the grinding of the sea and sand, and fragments lie along the shore which are 

 worn down perfectly smooth. Other specimens are much roughened by nu- 

 merous small holes drilled in the shell by various worms which enter them for 

 protection. The.y are sometimes vised as food liy the natives, either cooked or 

 raw, and are known to them as kupakala. 



Gasteropods, Including Snails, Slugs, Whelks, Cowries, Etc. 



In a book of this character it is obviously impossible to give more than the 

 briefest mention of some of the more common and interesting of the several 

 hundred species of gasteropod moUusks that have been reported from the 

 Hawaiian Islands. However, it is hoped that by reference to the accompanying 

 figures and the brief description given of the more common species occurring 

 in the waters about the islands, that many of the shells found along the shore 



'^^Lioconcha )iirrnffj,,j)l,irn. ^i Teiuis reticuUittt. '^^ Cnrdiiim arbiter. ^' CJinmida!. 



