658 CRETACEOUS PALEONTOLOGY. 



shell surface. Markings of the posterior half of the shell un- 

 known. 



Remarks. Casts of the irregular burrows of this species are 

 sometimes of common occurrence in the Merchantville clay, pen- 

 etrating masses of fossil wood, and on tracing these burrows 

 to their termination casts of the shell can usually be found, some- 

 times in excellent condition. Some masses of the tubes are all 

 much smaller than those in other masses, but all the tubes in 

 one group are usually of approximately the same dimensions. 

 It was at first thought possible that the different sized tubes indi- 

 cated different species, but the shells are all essentially the same, 

 whether from large or small tubes, in all masses observed in the 

 Merchantville clay-marl. A mass of essentially identical tubes 

 has been found in the Marshalltown clay-marl, however, asso- 

 ciated with many individuals of Martesia bisulcata, which have 

 a very different shell, described in this report as Turnus kiimmeli. 

 Other similar tubes occur sometimes in the Navesink marl, but 

 the accompanying shells have not been observed, these tubes, 

 however, seem to be straighter, and they probably belong to an- 

 other species. 



The type specimen of T. irregularis is without data as to local- 

 ity or horizon, and the description of the shell itself is too meagre 

 to be of any use in identification. Inasmuch, however, as the 

 Merchantville clay-marl is the horizon where burrows of this 

 sort most frequently occur, and as Gabb described numerous 

 fossils from this horizon in Burlington County, New Jersey, it 

 is altogether probable that the type specimen is specifically iden- 

 tical with the shell here described. 



Morton evidently applied the name Teredo tibialis to all the 

 Teredo-like tubes he found in New Jersey, but the name is still 

 retained for the tubes like those which he illustrated, which are 

 found only in the Vincentown limesand. The specimens which 

 he referred to from "the friable marls" which are preserved as 

 "casts in lignite" were in all probability representatives of the 

 species T. irregularis. 



The type of Teredo contorta Gabb, which is preserved in the 

 collection of the Philadelphia Academy of Science, has been care- 



