86 INVERTEBRATA OF MASSACHUSETTS. 



ridges being crowded and rising into thin, sharp plates, most con- 

 spicuous at the ends ; the central portion is nearly smooth. There 

 are also minute lines, radiating from the beaks to the margin, 

 most conspicuous on the beaks, where they form a lattice-work 

 with the concentric lines ; color a dirty-white, except the smooth 

 portion of the disk, which is dark-violet ; within pure white ; 

 muscular impressions deep, united by a well-marked palleal im- 

 pression which has an acute-angled, not very deep sinus ; the 

 margin outside the impressions is more or less of a beautiful deep- 

 violet hue ; basal and anterior margin crenulated. Length 3 

 inches, height 2J inches, breadth 2 inches. 



Brought from Wellfleet and other towns on Cape Cod in con- 

 siderable quantities to Boston market. It is found more abun- 

 dantly to the South, and in New York and Philadelphia markets 

 supersedes the use of the Mya arenaria almost entirely. While 

 it may be found in greater or less abundance in all the region of 

 Cape Cod, and scantily in all parts of Massachusetts Bay, I 

 cannot learn that it is ever found north of Cape Ann. 



The shell is easily known by its size and weight, and by its heart- 

 shaped form when resting upon its point. It is about the same size as 

 Cyprina Islandica, from which it is distinguished by the sharp ridges 

 on its surface, and by the want of an epidermis ; also by the violet- 

 colored border of the interior of the valves. This mark, however, is 

 not constant. In young shells it is wanting, and also in very old 

 shells the color is often obscured by a thick, white glazing. Fisher- 

 men say, that those found outside Cape Cod, in the region of Chatham, 

 are always devoid of it. The shell has become quite famous from 

 the fact that, from its purple edge, the aborigines manufactured their 

 purple wampum ; while the white wampum was made of various 

 species of shells. 



It is known in Massachusetts under the name of Quahog. The 

 upper outline of the figure represents this shell. 



VENUS NOTATA. 



Shell ovate-orbicular, inequilateral, posterior side truncated ; 

 surface with concentric, sharp ridges, mostly wanting on the disk ; 

 color yellowish or greyish-white, and with fawn-colored, zigzag 

 markings ; interior wholly white. 



FIGURE 52. 



