EXTERNAL CHARACTERS. 311 



D. rumphii [= scapula] might be raised so as to close th6 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 

 (Vayssiere, 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, mth a deep posterior sinus. The dorsal cuticular portion is well devel- 

 oped and of a Ught 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. 



