190 PALEONTOLOGY OF NEW JEESEY. 



Formation and locality. — In the Lower Green Marls at Marlborough, 

 New Jersey. In the collection at Rutgers College, New Brunswick, New 

 Jersey. 



Genus MAETESIA Leach. 



Martesia (Pholas) cretacea. 



Plate XXV, Figs. 20-23. 



PhoUis cretacea Gabb. Jour. A. N. Sci., new ser., Yol. IV, p. 393, PL LXVITI, Fig. 18. 



Proc. A. N. S., 1861, 324. 

 Martesia cretacea Gabb. Proc. A. N. S., 1876, p. 304. 



The tubes or casts of tubes from which this species was described are 

 from three-fourths of an inch to one and a quarter inches in length by about 

 three-eighths of an inch in diameter at the larger end of the largest. The 

 basal end is convex and the shaft of the tube regularly tapering. These 

 perforations have been in wood, which is now replaced by pyrite, and none 

 of them show any indications of the shell or markings by which its nature 

 can be determined. There is, however, a specimen in the Academy's collec- 

 tion, marked as of the same species in what appears to be Mr. Gabb's hand- 

 writing, which not only shows the general form of the shell but also some 

 sHght remains of the surface marking. The former is extremely ventricose, 

 clavate in front, and gradually but rapidly tapering behind, with distinct 

 incurved beaks and a shghtly marked mesial line of perceptible width sep- 

 arating the anterior and posterior portions of the valves. The antero-basal 

 area is triangular, and indistinctly marked. Anterior section of the valves 

 marked with strong undulations which have a strongly upward direction 

 from the mesial constriction towards the anterior end, while on the posterior 

 section they are parallel to the margin of the shell. The shell is somewhat 

 exfoliated, and therefore the surface markings cannot be so distinctly made 

 out as it would be desirable. 



Formation and locality. — The tubes used in the original description and 

 figured on our plate came from Raritan Bay, New Jersey. The shell, how- 

 ever, is simply marked *'Cret, N. J.,'- like so many of the specimens used 

 by Mr. Gabb, so that one is left in some degree of doubt as to what bed they 

 may have been obtained from 



