CEPHALOPODA. 767 
Piloceras newton-winchelli.] 
Class CHPHALOPODA. 
Order TETRABRANCHIATA. 
Suborder NauTiLorpEA. 
Family ENDOCERATID At. 
Genus PILOCERAS, Salter, 1859. 
PILOCERAS NEWTON-WINCHELLI, Sp. nov. 
PLATE XLVII, FIGS. 1—3. 
Two specimens preserved in a white chert indicate a small undescribed species 
of this genus. The more complete of the two is obliquely fusiform, slightly arcuate 
on the siphonal side, and bears sixteen septa which are very oblique on the upper 
part but lose this obliquity toward the apex; the direction of the earliest septum is 
nearly transverse. The obliquity of the later septa is so great that the last septum 
exposed, in crossing the shell from the dorsal to the ventral side traverses the depth 
of five air-chambers on their antisiphonal exposure. The length of this specimen 
is 31 mm. and its width at the top measured along a suture, 21 mm; the transverse 
diameter at the top, 17 mm; at the base 7mm. All the air-chambers are deepest 
at the antisiphonal edge. At the top of the specimen is the opening of a wide 
siphonal cavity. A longitudinal section of the specimen along the axis of this 
cavity shows some interesting points of structure. The mouth of the cavity is 
broad at the top, covering nearly one-third of the entire diameter of the shell. Its 
actual and relative diameter lessens, however, toward the apex. The position and 
relative size of the sipho and the difference in the direction of the septa on the two 
sides are shown in the accompanying figure. This cavity is not filled by a solid 
accumulation of siliceous matter, but is more or less cavernous. The siphonal 
walls, however, are encrusted and distinctly retained. It is very clearly evident 
from this section that the septa are not coalesced with the siphonal wall (ws). The 
edge of each septum lies close against, usually in actual contact with a thickened 
