8o MURDOCH : ANATOMY OF ASHMUNELLA. 



even and slightly reflexed margin, with a small lappet at the respira- 

 tory pore. Tentacles black, the inferiors appear to be very small ; 

 labial projections well marked and triangular in outline. Generative 

 orifice a little below and slightly posterior to the right tentacle. 



Internal An.\tomy. 



The Jaw and Radula (PI. vii, figs, i, 2). — The jaw is arcuate, 

 stout, with five or six slightly unequal, broad ribs in the middle area 

 and the ends with a number of small riblets. The dentition has the 

 formulae varying from 25 — i — 25 to 27 — 1 — 27. The central teeth 

 with stout mesocones, having well developed cutting points and small 

 right and left side cusps ; laterals with meso- and ectocones, the latter 

 small and the basal plates produced on the outer sides. From laterals 

 to marginals the change is gradual, the latter have the mesocones 

 bifid, and as they proceed outward the basal plates become shorter 

 with frequently two outer thorns, and occasionally three from the 

 splitting of a thorn. 



l^he Alimentary Canal (PI. vii, fig. 3). — The buccal mass has the 

 usual shape ; enveloping the oesophagus are two salivary glands, inti- 

 mately united along their inner edges, which gives to them the appear- 

 ance of a single gland with two ducts, the latter empty into the buccal 

 cavity in the usual position. The stomach forms a comparatively 

 large elongated sac, its posterior end is curved forward and receives 

 the right and left bile ducts. The intestine passes forward until arriving 

 at the posterior margin of the kidney, when it curves to the right and 

 then back through the folds of the liver, after which it again passes 

 forward, and terminates in a long, narrow rectum ; it thus divides the 

 left lobe of the liver into three irregular shaped lobules, from each of 

 these lobules is a bile duct, but all unite to form a single duct before 

 opening into the stomach. 



Tlie Pallial Organs, etc. (PI. vii, fig. 3). — The kidney is long and 

 narrow, in length nearly four times its width, slightly more than two 

 and a half times the length of the pericardium, and rather more than 

 half the length of the pulmonary chamber. The ureter arises from 

 the left anterior side of the kidney, follows the right margin, on which 

 it partially rests, back to the posterior end, then curving to the right 

 it forms a narrow tube and proceeds forward parallel with the rectum, 

 terminating a little in front of the respiratory orifice. The great 

 efferent vessel is conspicuous and runs direct to the auricle, its 

 numerous branches collect the blood from the right anterior corner, 

 middle area, and greater portion of the right side of the pulmonary 

 chamber; alternately with the efferent branches are the afferent vessels 



