115 



ARCA quadrisulcata. 

 TAB. CCCCLXXllL— /g-. 1. 



Spec. Char. Twice as wide as long^_, convex, lon- 

 gitudinally striated ; anterior side truncated, 

 defined by a keel, and marked by four deep 

 furrows ; posterior side small, rounded ; mar- 

 ginal sinus large. 



The sinus in the margin of this fossil shows it to be an 

 Area, although it is otherways so badly preserved that 

 its teeth cannot be discovered, and it might be taken 

 for a CucuUaBa : the four ribs between the furrows on the 

 anterior side are a good character to distinguish the spe- 

 cies by ; the longitudinal striae are crossed by the lines 

 of growth, and give the surface a rugged appearance. 

 Found in the Pisolite of Malton. 



ARCA cancellata. 

 TAB. CCCCLXXIIL—Zg^. 2. 

 Spec. Char. Twice as wide as long, convex, lon- 

 gitudinally and transversely sulcated ; ante- 

 rior side defined by a keel, truncated ; poste- 

 rior side rounded ; marginal sinus short but 

 deep ; beaks nearly close. 

 Syn. Conch. Arcites cancellatus. .Martin Pet. 

 Derb.pl. 44. Jig. 7. 



1 HE front and back are parallel; the anterior side has 

 many sulci of an equal depth with those upon the rest of 

 the surface : in other respects it much resembles the last. 

 From the Derbyshire Limestone, apparently the same 

 specimen that was figured by Mr. Martin. 



ARCA pulchra. 

 TAB. CCCCLXXIIL— /g. 3. 



Spec. Char. Transversely ovate-elongated, de- 

 pressed, finely striated, anterior side rather 

 impressed, obliquely truncated ; beaks close. 



JNearly twice as wide as long; the striae are very 

 uniform and close together ; the valves are rather flat in 

 the middle. 



Drawn from the Rev. Mr. Cookson's collection of 

 Ancliff fossils. Although there is hardly any appearance 

 of a sinus in the margin, this is placed as an Area be- 

 cause it has no transverse elongated teeth in the hinge, 

 those nearest the extremities being longitudinal : it is 

 however one of the links that unite the two Genera. 



