KUNGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 52. N:o (6. 33 
there branches off, immediately after its outset from the heart, an arteria gastrica, 
which descends on the left body side, similarly in Chama and Pseudochama, to the 
left of the intestine, towards the stomach; here it bifurcates and descends with one 
arm on each side of the duodenum. The principal trunk of the anterior aorta passes 
on above the stomach (in Pseudochama cristella to the left of it) and along the left 
side of the oesophagus (similarly in Chama and Pseudochama), from where it gives 
off a branch to the anterior adductor and one into the foot. — 'The posterior aorta 
presents nothing of interest; it sends a ventral trunk downwards between the nephri- 
dia and the posterior adductor and one along the under side of the rectum towards 
the siphons. — As to the veins, it has already been described how they are arranged. 
It remains only to say that a special pallial vein carries the blood from the mantle 
directly into the auricle. 
The intestinal canal. The stomach, which follows behind the simple oeso- 
phagus, presents in all the present forms great resemblances, but there are differ- 
ences as to the coecal appendages and the liver ducts. Pseudochama cristella has a 
very small coecum on the posterior side of the stomach, while in both the Chamas 
this attains more considerable size. Further, in P. cristella no lateral coecum of the 
stomach is present (the absence of this is characteristic of the whole genus Pseudo- 
chama, cf. above). this feature being confined to the genus Chama. Between the 
two species Ch. lazarus and Ch. reflexa there exists the difference that in the last- 
named we find, as the rule, a single principal liver duct (so even in Pseudochama 
cristella), while Ch. lazarus has two. For the rest, nothing of interest is to be noted. 
In all the three present forms the duodenum has a narrow furrow to the left and 
a larger one (corresponding to the crystalline coecum) to the right;' in its lower end 
the duodenum passes into the intestine through a simple flexure, and this, later on, 
pierces the ventriele and leads to the anus. 
The liver surrounds the stomach not only on its frontal and lateral, but also 
on its posterior and superior sides. 
The nervous system. GRIESER has described the organization of this system 
for Ch. pellucida and the same conditions that he has found prevail in all Chamidae 
(Chama as well as Pseudochama). A distinet buccal ganglion is present beneath each 
cerebral centre, by a suboesophageal commissure combined with that of the other 
side. There is also a median commissure between the cerebrovisceral connectives in 
front of the pericard, established between the genital nerves, which here emanate 
from the nerve cords. 
As to the genital organs, all Chamidae are gonochoristic; the folliculi fill all the 
visceral hump outside the liver and intestinal canal; the genital pores have somewhat 
projecting and muscular lips. 
The nephridia were briefly described by me in 1912. They are situated 
behind the pericard and in front of the posterior adductor, and extend in a 
dorso-ventral direction up to the sides of the rectum ; the left one is highest in Chama, 
1 Similarly in Chama and Pseudochama; GRIESER (1913) states for Ch. pellucida the reversed position. 
K. Sv. Vet. Akad. Handl. Band 52. N:o 16. 5 
