170 PALEONTOLOGY OF NEW JERSEI. 



He remarks, that, among the several specimens found, "none was found 

 attached to shells or other substances," but admits that none was found 

 entire. He does not state that any internal connection exists between the two 

 shells, and from his figures one would infer they were separate tubes merely 

 united by their external surfaces, but in close contact, and probably through- 

 out their entire length. I do not think the twin feature a good generic one, 

 unless there had been some internal connection between the inhabitants of 

 the tubes, but none appears to have existed so far as can be judged from the 

 figures, or from the author's description or remarks; therefore I think the 

 twinning of the shells either an accidental feature or not more than a specific 

 character, and presume the species is only a form of Serpula. Among the 

 fossils from the Cretaceous of New Jersey I have a specimen which closely 

 resembles Mr. Conrad's figured specimen, except in that it is not merely 

 attached to, but appears to have been partly imbedded in the substance of 

 a shell of Plagiostoma dumosum. The tubes, however, are clearly united and 

 conform to each other in curvature throughout a part of their length, and I 

 presume were specifically related to the North Carolina forms. Until better 

 evidence of the generic validity of the shell is obtained, I shall class this 

 one under Serpula, retaining Mr. Conrad's name parenthetically for the 

 present. I have tried to obtain the loan of the type specimen of the genus 

 from North Carolina, but owing to the absence of persons having charge of 

 the collections to which it belongs, I have not been able to see it. 



DiPLOcoNCHA (Serpula ?) cretacea?. 



Plate XX, Fig. 25. 



Diploconcha cretacea Conrad: Geol. North Carolina, vol. 1, 1875, appendix, p. 12, 

 PI. II, Fig. 26. 



Tubes apparently duplicate, the two nearly conforming to each other 

 in curvature; in contact, at least for a portion of their length, irregularly 

 arcuate and very slightly increasing in diameter; surface lamellose where 

 partially exfoliated and apparently concentrically and longitudinally lined 

 where perfect. 



The specimens have the appearance of Serpula tubes and, in their 

 earlier stages of growth, have been recumbent upon or imbedded in the sub- 



