PLATE IV. 
Spirula peronii. 
—Right side ; the walls of the mantle and of the episoma behind it are cut away. 
a. Posterior limit of the pallia! cavity. 
g.s. Ganglion stellatum. 
I.m.r. Retractor muscle of the infundibulum.—Other letters as in the foregoing 
plates. 
—Right side ; dissection carried further. 
a, b. Style introduced into an apparently natural aperture on the inner side 
of the stem of the right branchia. 
hr. Stump of the stem of the right branchia. 
hr.a. Afferent branchial vessel. 
br.h. Branchial heart. 
c.s. Cardiac sac of the stomach. 
o.m. Root of the ovary. 
w". Passage connecting the right and left divisions of the viscero-pericardial 
cavity.—Other letters as before. 
—Left side ; the wall of the episoma removed. 
a. The visceral wall of the pallial cavity cut away. 
b. Wide artificial opening. 
ov. Ova. 
—Aspect of fig. 3, showing the contents of the viscero-pericardial cavity after the 
mass of the ova was removed. 
a. Appendage of the left branchial heart. 
b. Style introduced into an artificial opening of the viscero-pericardial cavity. 
br.h'. Left branchial heart. 
o. d. Oviduct. 
p. c. Pancreatic caeca. 
p.s. Pyloric spiral sac of the stomach. 
p.t.n. “ Peritoneal” sac.—Other letters as before. 
—Upper part of the same aspect as fig. 4, with the left branchia turned down. 
a. Style. 
br.a. Afferent branchial vessel. 
M. Projection formed by the left accessory nidamental gland. 
w'. Artificial aperture in the viscero-pericardial cavity. 
