40 NILS HJ. ODHNER, MOLLUSCA. 
acea. Among them it takes a special position in the respect that both male and 
female organs have a common exterior opening, situated just beneath the end of the 
pericard and just opposite to the nephroproct (n.). It is a simple pore with some- 
what projecting margins. 
The nervous system. A remarkable fact is the presence (just as in Chamidae) 
of a large and distinct buccal ganglion behind each cerebral centrum, connected by 
means of a distinct and continuous suboesophageal commissure to that of the oppos- 
ite side. The right cerebral ganglion is situated higher up than the left one, as a 
consequence of the mode of attachment of the shell. For the rest, the nervous 
system exhibits no peculiarities. There is no median commissure between the cere- 
brovisceral connectives in front of the pericard, as in Chamidae. The pedal cords are 
very feeble and the pedal ganglia are coalesced to a single centre. 
The nephridia. These are situated behind the pericard and before the poster- 
ior adductor and are extended in a dorso-ventral direction from the side of the 
rectum down to the visceral ganglion. The right one lies somewhat higher than the 
left, as a consequence of the inequilaterality of the body. Each external sac is 
heavily and minutely lobed in all its outer walls, but the inner (median) wall is 
even. The epithelium lining the external sac forms a simple layer and each cell is 
occupied by a large rounded concretion of a deep brownish colour; all such particles 
are of uniform size. The external sacs debouch into the mantle cavity by means 
of simple pores (fig. 5.) with muscular margins opposite and close to the genital 
orifices, and are in very short communication (co.) with each other above the peri- 
cardial tubes. These (p. ¢.) emanate with rather long, strongly ciliated funnels from 
the lateral corners of the pericardium; the funnels converge inwardly, widen some- 
what to a sort of ampullae with smooth and even walls lined with ciliated epithelium, 
which are continued upwards by the very narrow pericardial tubes; these run, slightly 
winding, turned towards each other and separated only by the renal sinus, till they 
debouch into the upper third of the external sacs. 
As a whole, the nephridia of this species are very similar to those of Chamidae, 
especially of Pseudochama, but they differ in the smooth-walled ampulla, the some- 
what shorter pericardial tubes, and the presence of large concretions in the external 
sacs. The mentioned characteristics are confined to forms of Anatinacea (Pandora, 
Lyonsia, Thracia), from which, however, the short communication of the external 
sacs serves to distinguish the present form (cf. ODHNER 1912). 
Sensory organs. Immediately above and without the pedal ganglia are to 
be found the large statocysts (fig. 5 st.). They each contained large statolith and 
many small statoconia. The co-existence of these features is characteristic of Anatin- 
acea. The statoconia showed the peculiarity of being assembled in the upper left 
part of the statocyst, either as a result of the right-sided fixation or else due to some 
temporary conditions at the moment of the preservation. 
On the right side of the body there was to be observed a well-developed sens- 
ory organ, situated on the mantle just at its junction with the siphonal fold and 
extending from the median part of the inspiratory sipho up to the outer base of the 
