534 
bread, shallow lobes, but in some specimens the sutures are nearly 
straight or may retain slight saddles on the venter. 
The siphuncle is extracentrodorsan. 
NEPHRITICERAS CAVUM. 
Naummusccayus (Pal. JV. Y., v, Pt. ii,.Pl evi): 
The fragment of the neanic stage, figured by Hall, has the 
nephritic whorl and similar sutures to the full grown of Wephritice- 
ras bucinum, but the dorsal lobes are deeper perhaps and more 
V-shaped. ‘The septa are different in being much more widely sep- 
arated, but are otherwise similar to those of the later stages in 
Nephriticeras bucinum. I find in my notes that the impressed 
zone occurs after the dorsal lobes are formed and at an earlier stage 
than in ducinum. 
Siphuncle is unknown. 
NEPHRITICERAS ACREUM. 
NAUTILUS ACR&US, Hall (Pal. WV. Y., v, Suppl., Pl. cix). 
The fragment of the neanic stage, figured by Hall, shows the 
nephritic outline impressed zone and ridges similar to those of the 
older stages of Wephriticeras bucinum occurring at an earlier stage 
than they do in Wephriticeras cavum.* 
NEPHRITICERAS MAGISTER. 
NAUTILUs MAGISTER, Hall (Pa/. WV. Y., v, Pls. Ixii, cvii, cviii). 
The large fossils of this species which I have examined have not 
afforded me any information with regard to the young, but the 
nephritic form of the whorl, the impressed zone and large beaded 
siphuncle dorsad of the centre show that the species belongs in the 
same genus with Wephriticeras bucinum. 
This species may have either slight ventral lobes or saddles on 
the venter. 
NEPHRITICERAS MAXIMUM. 
NavuTILus MAxiMus, Hall (Pad. WV. Y., v, Pt. ii, Pls. lxxiii, Ixxiv). 
This is like Wephriticeras magister, known only through large 
fossils, but the young of the specimen figured by Hall on PI. lxxiii 
*T regret very much that in finishing this paper I have had no opportunity to revisit 
Prof. Hall’s collection and study again his old and new materials. It is not improbable 
that his fine series of Nephriticeran species may show that the impressed zone was pres- 
ent as a dorsal furrow in the paranepionie substage of some of the more inyolute and 
tachygenic shells. 
