MOLLUSCA 



Class CEPHALOPODA 



subclass TETRABR.ANCHIATA 



Order NAUTILOIDEA 



Suborder ORTHOCHOANITES 



Family NAUTILIDAE 



Genus EUTREPHOCERAS Hyatt 



[Proc. Am. Phil. Soc. for 1893, 1894, p. 555] 



Type. — Nautilus dehayi Morton. 



" This genus includes these forms like the type Eutrephoceras dekayi, 

 which have globose ananepionic substages, increasing subsequently with 

 great rapidity in all their diameters. The ananepionic and meta.ne- 

 pionic substages are highly tachygenic and these shells have very small, 

 and often hardly perceptible and much flattened, umbilical perforations. 

 The siphuncles are subdorsal from the apex through the nepionic stage 

 in some species, in others this position is not maintained, but the siphuncle 

 is generally in later stages near the dorsum and in the ephebic stages it is 

 dorsal of the center. 



" The nepionic stage has longitudinal ridges and transverse bands, the 

 former disappearing in adults which are smooth. The form of the whorl 

 in section is nephritic from an early age and changes but little throughout 

 life. The sutures are almost straight, having but slight ventral lobes, 

 broad ventro-lateral saddles, lobes on the umbilical zones and deep lobes 

 in the zone of impression. There are no annular lobes at any stage of 

 development." — Hyatt, 1894. 



Etymology: evrpeipTfs, clasping around. 



