YOLDIA. 



155 



Fi-. 462. 



somewhat pearly; cartilage-pit small; the series of teeth, extending 

 more than two thirds the length of the shell, is slightly bent at the 

 pit ; teeth prominent, most 

 so at the middle of each 

 side, their summits forming 

 a regular arch, twenty-two 

 on the anterior, and eighteen 

 on the rostrated side, exca- 

 vated on their outer faces ; 

 impressions quite oln'ious, 



. , y. liuiiitiita. 



Length, one and nme tenths 



inches ; height, nine tenths of an inch ; breadth, five tenths of an 



inch. 



Found in various parts of Massachusetts Bay ; Boston Harltor, in 

 two to ten fathoms mud ; Eastport, in six fathoms ( SU/npsoti) ; 

 Vineyard Sound (Ag-assiz) ; Long Island Sound (Prime) ; Port- 

 land Harbor (Mig-hc/s); Fishing Banks {Willis); Capuchin, Mar- 

 couin, St. Anne (Bell) ; Nordland (MeAndreiv). 



Animal with siphons united, the anal one translucent, the branchial 

 opa(iue white, both fringed at oi)cnings ; edges of foot-lobes simple. 



This beautiful shell may be distinguished from other species of 

 our coast by its length, which is more than twice as great as its 

 height. Its posterior portion is also more narrowed than in other 

 species. The dimensions given above are those of a specimen 

 larger than is ordinarily found. But I have a single valve sent mo 

 l)y Dr. Mighels of Portland, which he dredged in the harljor of that 

 place, where he found them aljundantly, measuring two and three 

 tenths inches in length, and one and one tenth inches in height. 

 He informs me that the animal is very active, and that it lea})S to an 

 astonishing height, exceeding in this faculty the scallop-shells. (See 

 Catal. of the Shells of Maine, 16). 



Yoldia obesa. 



Shell very small, oval, smooth, beaks nearly central ; teeth small, ten in front 

 and twelve behind. 



Leda obesn, Stimpson, Proc. Bost. Soc. Nat. Hist. iv. 1.3 (1851) ; Shells of New England, 



10, pi. 2, fig. 1 ; Clieck Lists. 

 Nucula navic}ilans, Mighei.s (not Couthouy), Shells of Maine, 17, according to Adams. 



Shell quite small, thin and fragile, of an elongated oval form, the 

 posterior part, which is a little the longer, being obtusely rounded 



