MARYLAND GEOLOGICAL SURVEY 593 



Description. " The dimensions of an average specimen, a left valve, 

 are : Height 30 mm., width 27.5 mm., convexity 4 mm., length of hinge 

 line 14 mm. The body of the shell broadly subovate in outline ; the beaks 

 situated a little back of the middle of the hinge line, the auriculations mod- 

 erately large and sharply differentiated, the anterior ones somewhat larger 

 than the posterior, the cardinal slopes diverging from the beak at an angle 

 of 90 or a little more, nearly straight or slightly concave, terminating at 

 the sides of the shell above the middle of its height. The valves sub- 

 equally depressed convex, the right valve if anything slightly flatter than 

 the left, with a moderately deep byssal sinus. Surface of both valves nearly 

 smooth, marked only by fine concentric lines of growth which continue 

 across the auriculations, and on the anterior ear of the right valve become 

 stronger than elsewhere on the shell. One imperfect specimen which 

 seems to be a member of this species had a height, when complete, of about 

 50 mm., but the dimensions given above are those of a specimen of about 

 average size. Some of the smaller individuals do not exceed 12 mm. in 

 height. With the growth of the shell the proportionate width seems to 

 increase. This species is unlike any of the other Pectens in these New 

 Jersey faunas, but in general form and size the shells most closely resemble 

 some individuals of Pecten bellisculptus Con. ; the two species can always 

 be distinguished, however, by their surface markings." Weller, 1907. 



Type Locality. Cliffwood Point, Middlesex County, New Jersey. 



A cast of a single valve which presents no characters by which it can be 

 separated from Pecten cliffwoodensis Weller was collected at Arnold 

 Point, on the Severn River in Anne Arundel County. 



Occurrence. MATAWAN FORMATION. North shore Eound Bay, Severn 

 Eiver, Anne Arundel County. 



Outside Distribution. Magothy Formation. Cliffwood clay of New 

 Jersey. 



PECTEN CONRADI (Whitfield) Johnson 



Pecten simplicus Conrad, 1868, Cook's Geol. of New Jersey, p. 725. 



(Not Pecten simplicius Conrad, 1860, Jour. Acad. Nat. Sci., Phila., 2d 



ser., vol. iv, p. 283, pi. xlvi, fig. 44.) 

 Sinsyclonema f simplicia Conrad, 1869, Am. Jour. Conch., vol. v, p. 99, pi. ix, 



fig. 20. 



