130 SYSTEMATIC PALEONTOLOGY 



will serve, we believe, in distinguishing it from all other described forms 

 of the genus. Corresponding protuberances are indicated in two of 

 Lienenklaus' species from the Miocene and Upper Oligocene of Ger- 

 many, viz., in C. denticulatum very faintly, in C. caudatum more dis- 

 tinctly. This indication, however, consists of little more than what may 

 be produced by the development of a median sulcus, so that there is still 

 left a considerable gap between them and C. nodosum. Some resem- 

 blance is noted in comparing C. nodosum with Cythere harrisiana Jones, 

 but we are not prepared to say that it indicates genetic relationship. How- 

 ever that may be, there can be no question concerning the specifiic dis- 

 tinctness of the two forms. 



Occurrence. — Chesapeake Gkoup. James Eiver, Ya. Probably also 

 in Maryland. 



Collection. — U. S. National Museum. 



suBKiNGDOM MOLLUSCA. 



Class CEPHALOPODA. 



Subclass TETRABRANCHIATA. 



Order NAUTILOIDEA. 



Suborder ORTHOCHOANITES. 



Family NAUTILID/E. 



Genus NAUTILUS Linne. 



Nautilus (?) sp. 

 Plate XXXIX, Fig. 1. 



A single fragment representing the peripheral portion of a septum of 

 a large Nautiloid form has been found. 



Length, 30 mm. ; width, 25 mm. ; depth, 6 mm. ; thickness, 1.3 mm. 

 Occurrence. — Calvert Formation. Plum Point. 

 Collection. — Cornell Universitv. 



