170 PALEONTOLOGY OF NEW JERSEY. 
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 havea 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, 
Pl. 1, 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 pertect. 
The specimens have the appearance of Serpula tubes and, in their 
earlier stages of growth, have been recumbent upon or imbedded in the sub- 
