74 A. M VeiTill — Study of the family Pectinidoe. 



or eight broad rounded radial ridges covered, like the interspaces, 

 with rough radial ribs. The sculpture of this variety is figured on 

 pi. xvi, figs. 4-5b. This variety is connected with the common form 

 by intermediate specimens. 



This species is found at and just below low-water mark, as well as 

 in deeper water, down to 179 fath., in the Bay of Fandy and north- 

 ward to Greenland and Iceland, etc. It is common and of large size 

 on the fishing banks off Nova Scotia and Newfoundland. Further 

 south it occurs in 20 to 100 fathoms, as far south as Cape Cod. 

 Dead shells were takfen off Martha's Vineyard in 69 to 194 fath. 



It is found as a Post-pliocene fossil in Maine, New Brunswick, 

 Canada, Labrador, Greenland and Northern Europe. 



Chlamys Benedict! Yerrill and Bush, sp. nov. 



Shell small, higher than long, with the posterior auricle much 

 longer than the anterior, with a deep byssal notch in the right valve. 

 The dorsal margin is straight and only slightly oblique ; the anterior 

 auricle, in the right valve, is decidedly angular, with its outer end 

 slightly incurved and serrated by the terminations of the radial ribs. 

 The posterior auricle is considerably prolonged and angulated at the 

 ixpper corner, obtusely rounded at the end and deeply notched where 

 it joins the main shell ; it has four strongly marked radiating ribs, 

 besides the dorso-marginal fold ; below these there is a slightly con- 

 cave space corresponding to the byssal notch. On the body of the 

 shell there are six or seven shai'p serrations along the lower margin 

 of the notch. In the upper valve the posterior auricle is broad and 

 decidedly angular, the dorsal and outer margin forming less than a 

 right angle ; its surface is covered with about five or six radiating 

 ribs decussated by more numerous and finer concentric raised lines, 

 the anterior and posterior margins of the body of the shell slope 

 about equally and form an acute angle ; the ventral mai'gin forms 

 a regular semicircular curve ; its entire surface on both valves is 

 covered by strongly raised, rather close radiating ribs, separated by 

 rather wider deep grooves. The interspaces are decussated by regu- 

 lar raised concentric lines ; these are scarcely apparent on the ribs 

 except on very young shells, but there are rather strong elevated 

 spine-like points, especially near the margins, arranged along the ribs 

 in pretty regular concentric lines. These become higher and more 

 pointed anteriorly, and are frequently nearly obsolete in the middle 

 portion of the lower valve ; in that case the ribs appear nearly 

 smooth and rounded. The ribs project at the margin as blunt points. 



