EXTERNAL CHARACTERS. 311 
D. rumphit [= scapula] might be raised so as to close the posterior opening 
completely, when the epipodial margins are closely appressed, thus converting 
the pallial cavity into a sac, open only in front. He suggests that the forcible 
ejection of the water contained in this cavity under such conditions might sud- 
denly propel the animal backward, as is done in the nearly related Notarchus 
(Vayssiére, 1885, p. 81) and in the Cephalopoda. No record has ever been 
made of any such habit so far as I am aware. 
The hypobranchial gland, or organ of Bohadsch, is a diffuse structure made 
up of an enormous number of tubules opening independently in the floor of the 
pallial chamber at the right of the genital opening and the spermatic groove. 
It extends from the anterior end of the chamber backward as far as the pos- 
terior end of the base of the ctenidium and the region of the rectum, the total 
area occupied being somewhat semicircular in outline, and reaching a length 
of 44.0 mm., and a width of 23.0 mm. The body-wall of this region is very 
spongy in texture, being made up almost entirely of the felted mass of gland- 
tubules, the actual integument being quite thin in this location. 
The external renal opening is a minute inconspicuous pore, situated below 
and near the posterior end of the base of the ctenidium. 
Shell.— The shell (Plate 4, fig. 2) is moderately large and strong, hatchet 
shaped, with a deep posterior sinus. The dorsal cuticular portion is well devel- 
oped and of a light amber color. The calcareous portion was somewhat broken, 
so that the exact limits of its extent forward and toward the right or younger 
margin could not be determined accurately. The spire is loosely coiled and 
heavily calloused and rough. Along the back the margin is rather broadly 
reflexed posteriorly, becoming narrower in front and disappearing before the 
anterior end of the shell is reached. Toward the apex this reflexed margin 
broadens and is continued into the apical calloused area. The margin of the 
sinus is similarly, but more narrowly reflexed. The shell is 54.0 mm. in extreme 
length by 31.0 mm. in width, with an approximate altitude of 6.0 mm. 
